We study the population size time series of a Neotropical small mammal with the intent of detecti... more We study the population size time series of a Neotropical small mammal with the intent of detecting and modelling population regulation processes generated by density-dependent factors and their possible delayed effects. The application of analysis tools based on principles of statistical generality are nowadays a common practice for describing these phenomena, but, in general, they are more capable of generating clear diagnosis rather than granting valuable modelling. For this reason, in our approach, we detect the principal temporal structures on the bases of different correlation measures and from these results we build an ad-hoc minimalist autoregressive model that incorporates the main drivers of the dynamics. Surprisingly our model is capable of reproducing very well the time patterns of the empirical series and, for the first time, clearly outlines the importance of the time of attaining sexual maturity as a central temporal scale for the dynamics of this species. In fact, an...
Carnivores face conflicts with humans, which has reduced their numbers and distribution. Carnivor... more Carnivores face conflicts with humans, which has reduced their numbers and distribution. Carnivores compete in intraguild predation systems, Subordinate predators usually avoid top predators through spatial or temporal separation. Coexistence requires a complex combination of resources and environmental conditions. In this study, we assessed the occupancy and temporal activity during night time of the jaguar (Panthera onca) and puma (Puma concolor) in the Serra da Capivara National Park (SCNP), located in the semi-arid Caatinga biome of Brazil. Felines face biological limitations in hot environments. We used camera-traps, occupancy models and temporal analysis to evaluate their patterns of habitat use, activity and interactions in SCNP between 2009 and 2011. We considered jaguar as dominant predator and puma as subordinate, and expected to find spatial and temporal avoidance between them. We found evidence of spatial and temporal coexistence. This coexistence could be a result of a restriction of niche separation between both species, influenced by the harsh conditions in the Caatinga, represented by a combination of extreme temperatures, scarcity of refuges to thermoregulate, an environment around SCNP with a high level of human disturbance and an apparent increase in prey due conservation policies. Crown
Resumo. A teoria dos jogos foi desenvolvida inicialmente para tratar proble-mas econômicos onde h... more Resumo. A teoria dos jogos foi desenvolvida inicialmente para tratar proble-mas econômicos onde haviam interações racionais entre os agentes. No entanto, aplicações dessa teorià a ecologia foram muito importantes, particularmente após a publicação do artigo seminal The logic of animal conflict, onde foi pro-posto o conceito de Estratégias Evolutivamente Estáveis. O objetivo desse estudó e realizar uma síntese dos conceitos de modelagem em ecologia baseada em teoria dos jogos, realizados a partir de Maynard Smith, com uma aborda-gem introdutória e interdisciplinar, partindo de ideias econômicas e avançando para temas mais aplicados como modelos que apontam para o fenômeno de seleção dependente da frequência. Palavras-chave: jogos evolutivos, seleção dependente da frequência, estratégias mistas, equação do replicador
The abundance of Guiana dolphins (Sotalia guianensis) in Guanabara Bay, Rio de Janeiro, Southeast... more The abundance of Guiana dolphins (Sotalia guianensis) in Guanabara Bay, Rio de Janeiro, Southeastern Brazil, was investigated during the period 2000–2015 using mark-recapture models applied to photo-identification data. A combination of Pradel's model and Pollock's robust design was applied to estimate abundance and other population parameters, such as apparent survival (), capture probability (p) and seniority probability (). Total population size was estimated by correcting the estimates derived from the Pradel robust design model for the proportion of marked individuals in the population. The corrected abundance estimates decreased drastically (37%) between 2000 (62, 95% CI 59–65) and 2015 (39, 95% CI 37–40), and can be explained by a combination of low survival and recruitment rates. Determining the ultimate causes for the decline in this Guiana dolphin population is difficult, but the likely reasons are of anthropogenic nature, such as by-catch, habitat degradation, intense traffic of vessels and exposure to immunosuppressive and endocrine-disrupting pollutants. We provide the first quantitative evidence of population decline in a delphinid from Brazilian waters. Conservation and management actions are urged to change this scenario. Other local dolphin populations in Brazil, which are exposed to the same impacts, may also be currently declining or are expected to do so in the near future. For this reason, we emphasize that anthropogenic impacts upon estuarine/coastal species that exhibit site fidelity warrant greater attention, because such impacts may lead to the same negative scenario observed in Guanabara Bay.
We study the population size time series of a Neotropical small mammal with the intent of detecti... more We study the population size time series of a Neotropical small mammal with the intent of detecting and modelling population regulation processes generated by density-dependent factors and their possible delayed effects. The application of analysis tools based on principles of statistical generality are nowadays a common practice for describing these phenomena, but, in general, they are more capable of generating clear diagnosis rather than granting valuable modelling. For this reason, in our approach, we detect the principal temporal structures on the bases of different correlation measures, and from these results we build an ad-hoc minimalist autoregressive model that incorporates the main drivers of the dynamics. Surprisingly our model is capable of reproducing very well the time patterns of the empirical series and, for the first time, clearly outlines the importance of the time of attaining sexual maturity as a central temporal scale for the dynamics of this species. In fact, an important advantage of this analysis scheme is that all the model parameters are directly biologically interpretable and potentially measurable, allowing a consistency check between model outputs and independent measurements. One of the main objectives in the field of population dynamics is to determine the extent of deterministic vs. stochastic forces in time series of abundance and population parameters. The deterministic share of the observed fluctuations is usually assigned to nonlinear density-dependent processes, which create regulatory and stabilising forces 1. Different theoretical and modelling frameworks have been used through the history of population dynamics , but time series analysis and autoregressive models are a frequent and natural choice, as the population size in the future is related to the population size in the past 2–4. A variety of time series analysis methods have been used in population dynamics to diagnose their structure and density dependence 5 , particularly successful in the analysis of empirical data of long lived taxa such as mammals 6–8. The approach proposed by Royama 9 combines diagnostic tools with the use of phenomenological models, and has increased the predictive power and understanding of the dynamics of intensively studied systems 10–12. In general, for sufficiently long time series, it is possible to use conventional autoregressive models or to apply other analogous methods which aim to determine a clear differentiation between deterministic and random components 13,14. The most common approach 9,15 uses a linear autoregressive model of order k , which relates the logarithm of the population abundance (y t) at different time steps: ∑ β β ε = + +. () = −
This article is a review of the developmental trajectory of the scientific reasoning on populatio... more This article is a review of the developmental trajectory of the scientific reasoning on population biology in small mammal studies led by Prof. Rui Cerqueira throughout his career. The multidisciplinarity joining ecology, demography, genetics, epidemiology, biogeography, taxonomy and systematics, and the different approaches guided by relevant ecological questions have always been present in his research projects which led to the progress of the knowledge described here. We report three empirical studies of long-term population biology: the study in Restinga de Barra de Marica, RJ, a pioneer study in many aspects at the time; the study in Sumidouro, RJ, developed in collaboration with the Fundação Oswaldo Cruz, RJ, related to the role of wild rodents in the transmission dynamics of schistosomiasis; and the study in Garrafão, municipality of Guapimirim, RJ. The latter arose from ideas generated in the study of Restinga de Barra de Marica on movements and population structure of some marsupial species and is still in progress, being one of the longest population dynamics studies of small mammals in Brazil. New and important results were obtained in these three projects using the capture-mark-recapture technique that permitted to obtain high quality data. The contribution of Prof. Cerqueira raised the field of mammalogy and in particular the population biology of small mammals in Brazil to a level of international excellence, both in terms of generating new knowledge and training human resources, as well as in terms of progress and sophistication of methodologies and analyses. (OBS: The article was published in portuguese)
Estimates of local population abundances, which require carefully designed sampling procedures, c... more Estimates of local population abundances, which require carefully designed sampling procedures, can provide valuable information on population size and density. Even though small mammals are one of the most widely studied vertebrate groups, many surveys have not recorded basic information to estimate local abundances, for instance catching effort. Here we suggest a simple comparative trapping frequency index that can be used as an alternative to the relative abundance index in data sets that only contain the number of species and individuals collected, thus lacking information on sampling effort. To compare trapping frequency and relative abundances we used capture records from more than four years, from seven species of rodents and two marsupial species collected by the Brazilian Plague Service. We calculated the trapping frequency index of each species as the proportion of trapped individuals per total of all individuals caught. We found that this trapping index was significantly correlated with a relative abundance index (number of captured individuals divided by number of trap nights). Our findings suggest that the proposed index may be useful for comparisons in situations where data on catching effort is lacking. The index may also provide a simple, though approximate quantification of relative local abundances, with possible applications in comparative studies (e.g. meta-analysis). We suggest that this index is used in studies that do not focus on obtaining accurate population parameter estimates, but which nonetheless contain data that can still offer a representative measure to compare local population abundances.
Effects of density dependence on animal movements have received much attention in ecology, but it... more Effects of density dependence on animal movements have received much attention in ecology, but it is still debated to what extent dispersal and movements in general are density dependent, and their potential contribution to population regulation processes. Here, we determine the occurrence and nature of density dependence in the movements of a Neotropical marsupial, the black-eared opossum Didelphis aurita Wied-Neuwied 1826. Using spool-and-line tracking devices, we estimated the tortuosity of fine-scale movements of 149 individuals by their fractal dimension D.We evaluated the relative importance of population size, reproductive or climatic seasons and reproductive maturity of individuals as determinants of movement tortuosity, using a model selection approach. Population size was the most important determinant of movement tortuosity, with season (climatic seasons for females, reproductive seasons for males) and reproductive maturity as secondary but also important variables.We detected a positive density-dependent effect on movement tortuosity, resulting in more intensive use of areas by individuals during periods of high population size. This positive association between movement tortuosity and population size is more likely to result from intraspecific competition, which forces individuals to explore their environment more intensively during high-density periods. Therefore, despite being density dependent, movements in D. aurita apparently do not contribute to population regulation mechanisms.
Population fluctuations are the result of the combined action of endogenous (feedback structure) ... more Population fluctuations are the result of the combined action of endogenous (feedback structure) and exogenous factors (large- and local-scale climate variables). In this paper, we used a 13-year time series to identify the feedback structure in a population of the brown 4-eyed opossum Metachirus nudicaudatus and to test a hypothesis on the effects of El Niño Southern Oscillation and rainfall using Royama’s theoretical framework. Metachirus nudicaudatus was regulated by a strong 1st-order negative feedback, with intraspecific competition for food resources as the probable factor governing the endogenous system. Contrary to our expectations, El Niño did not explain the marsupial dynamics better than 1-year lagged rainfall, that may operate in 2 different manners: as a nonlinear perturbation effect influencing the strength of density dependence (intraspecific competition and intraguild predation) or as a lateral perturbation effect influencing the carrying capacity of the environment.
The relative effect of survival and reproductive rates to population growth rate is e... more The relative effect of survival and reproductive rates to population growth rate is expected to be similar across species with similar life-histories. We employed a matrix population model and sensitivity and elasticity analysis to assess the absolute and relative importance of age-specific survival and fertility to population growth rate of Didelphis aurita (Didelphimorphia, Didelphidae) in a rural area of Rio de Janeiro, southeastern Brazil. The results were compared to expectations for mammals that mature early and have short generation time, such as D. aurita. Prospective analysis showed that changes in pouch young and juveniles survival would have large effects on population growth rate, relative to other vital rates, being the most critical time periods in the life cycle of D. aurita, whereas the effect of fertilities were always low. These findings do not fit to the observed pattern in mammals that mature early, where reproductive parameters have the largest relative influence on population growth rate. Although reproductive rates were characterized by a relatively small influence on population growth rate, they are still relevant because of their high variability and response to potential environmental disturbances. The first application of matrix population models to a neotropical rainforest marsupial provides information on marsupial demography and life-history strategy, increasing comprehension of this unknown group.
Studies on habitat selection based on the presence and absence of individuals still rarely includ... more Studies on habitat selection based on the presence and absence of individuals still rarely include the uncertainty of absence. With it, one can model the probability of detec- tion, which is a parameter of interest especially when dealing with species where non-detection is common. Here, we per- formed an analysis of microhabitat selection of a New World marsupial (Marmosa paraguayana, Tate 1931)—an arboreal species endemic to the Brazilian Atlantic forest—accounting for false absence. We found empirical evidence supporting one of our hypotheses: the angle of the terrain’s inclination at a site positively affects detection probability. This is probably due to the fact that, at an inclined site, the area available to the animals tends to be larger and the proba- bility of detection of M. paraguayana would be higher, due either to greater local abundance or increased frequency of moving. The probability of resource use was heteroge- neous, or rather, not constant in space, but constant in time. We found weak evidence for the correlation between the canopy volume and the probability of resource use. However, we observed a tendency in the estimates of site-specific probability of resource use: the highest values of the probability of resource use appeared in the upper part of the study grid, where the canopies were denser as well as more closed. Thus, this specie’s prob- ability of resource use possibly diminishes in habitats such as early secondary forest with tiny canopies.
A fundamental step in the emerging Movement Theory is the description of movement paths, and the ... more A fundamental step in the emerging Movement Theory is the description of movement paths, and the identification of its proximate and ultimate drivers. The most common characteristic used to describe and analyze movement paths is its tortuosity, and a variety of tortuosity indices have been proposed in different theoretical or empirical contexts. Here we review conceptual differences between five movement indices and their bias due to loca- tions errors, sample sizes and scale-dependency: Intensity of Habitat use (IU), Fractal D, MSD (Mean Squared Distance), Straightness (ST), and Sinuosity (SI). Intensity of Habitat use and ST are straightforward to compute, but ST is actually an unbiased estimator of oriented search and ballistic movements. Fractal D is less straightforward to compute and repre- sents an index of propensity to cover the plane, whereas IU is the only completely empirical of the three. These three indices could be used to identify different phases of path, and their path tortuosity is a dimensionless feature of the path, depending mostly on path shape, not on the unit of measurement. This concept of tortuosity differs from a concept implied in the sinuosity of BENHAMOU (2004), where a specific random walk movement model is assumed, and diffusion distance is a function of path length and turning angles, requiring their inclusion in a measure of sinuosity. MSD should be used as a diagnostic tool of random walk paths rather than an index of tortuosity. Bias due to location errors, sample size and scale, differs between the indices, as well as the concept of tortuosity implied. These differences must be considered when choosing the most appropriate index.
A population of the black-eared opossum, Didelphis aurita Wied-Neuwied 1826, was studied during 1... more A population of the black-eared opossum, Didelphis aurita Wied-Neuwied 1826, was studied during 1997-2006 by capture-mark-recapture in the Atlantic Forest in the state of Rio de Janeiro. Cohorts were established with females marked still in the pouch, classified into five age classes. Population parameters were estimated using life tables. Survival was type III and mortality was greatest in age classes I and II, just after weaning. Fecundity was inversely correlated with survival, reproductive value was inversely correlated with mortality and residual reproductive value was inversely correlated with fecundity. The intrinsic rate of increase was always close to zero and tended to be slightly negative. The black-eared opossum can be considered a good model species for this type of study.
A major difficulty in the application of probabilistic models to estimations of mammal abundance ... more A major difficulty in the application of probabilistic models to estimations of mammal abundance is obtaining a data set that meets all of the assumptions of the model. In this paper, we evaluated the concordance correlation among three population size estimators, the minimum number alive (MNA), jackknife and the model suggested by the selection algorithm in CAPTURE (the best-fit model), using long-term data on three Brazilian small mammal species obtained from three different studies. The concordance correlation coefficients between the abundance estimates indicated that the probabilistic and enumeration estimators were highly correlated, giving concordant population estimates, except for one species in one of the studies. The results indicate the adequacy of using enumeration estimates as indexes for population size when scarce data do not allow for the use of probabilistic methods. Differences observed in the behavior of enumera- tion and probabilistic methods among species and studies can be related to the exclusive sampling design of each area, species-specific movement characteristics and whether a significant portion of the population could be sampled.
The genetics and ecology of pumas are well documented in North America but there is a lack of stu... more The genetics and ecology of pumas are well documented in North America but there is a lack of studies in South America, especially in Brazil. By means of a noninvasive method, faecal DNA analysis, we estimated puma abundance in two protected areas embedded in a human-disturbed landscape in the north-east of São Paulo state, in south-east Brazil. In 8 months of mark–recapture faeces sampling, 15 individual pumas were identified using seven microsatellite loci. The estimated abundance of pumas with the Jolly–Seber open population model was 23.81 ± SE 6.22. This is the first estimate of the abundance of pumas in a human-dominated landscape in São Paulo state, the most populous, developed and industrialized state of Brazil. The absence of high-quality habitats in the north- east of the state, the absence of direct competitors and the high availability of prey in protected areas are probably contributing to the high number of pumas concentrated in a relatively small area (c. 260 km2). Our results will contribute to the long-term monitoring of this puma population and, combined with other ecological, behaviour- al and genetic data, will help guide conservation action to maintain a viable population of the puma in this region.
We study the population size time series of a Neotropical small mammal with the intent of detecti... more We study the population size time series of a Neotropical small mammal with the intent of detecting and modelling population regulation processes generated by density-dependent factors and their possible delayed effects. The application of analysis tools based on principles of statistical generality are nowadays a common practice for describing these phenomena, but, in general, they are more capable of generating clear diagnosis rather than granting valuable modelling. For this reason, in our approach, we detect the principal temporal structures on the bases of different correlation measures and from these results we build an ad-hoc minimalist autoregressive model that incorporates the main drivers of the dynamics. Surprisingly our model is capable of reproducing very well the time patterns of the empirical series and, for the first time, clearly outlines the importance of the time of attaining sexual maturity as a central temporal scale for the dynamics of this species. In fact, an...
Carnivores face conflicts with humans, which has reduced their numbers and distribution. Carnivor... more Carnivores face conflicts with humans, which has reduced their numbers and distribution. Carnivores compete in intraguild predation systems, Subordinate predators usually avoid top predators through spatial or temporal separation. Coexistence requires a complex combination of resources and environmental conditions. In this study, we assessed the occupancy and temporal activity during night time of the jaguar (Panthera onca) and puma (Puma concolor) in the Serra da Capivara National Park (SCNP), located in the semi-arid Caatinga biome of Brazil. Felines face biological limitations in hot environments. We used camera-traps, occupancy models and temporal analysis to evaluate their patterns of habitat use, activity and interactions in SCNP between 2009 and 2011. We considered jaguar as dominant predator and puma as subordinate, and expected to find spatial and temporal avoidance between them. We found evidence of spatial and temporal coexistence. This coexistence could be a result of a restriction of niche separation between both species, influenced by the harsh conditions in the Caatinga, represented by a combination of extreme temperatures, scarcity of refuges to thermoregulate, an environment around SCNP with a high level of human disturbance and an apparent increase in prey due conservation policies. Crown
Resumo. A teoria dos jogos foi desenvolvida inicialmente para tratar proble-mas econômicos onde h... more Resumo. A teoria dos jogos foi desenvolvida inicialmente para tratar proble-mas econômicos onde haviam interações racionais entre os agentes. No entanto, aplicações dessa teorià a ecologia foram muito importantes, particularmente após a publicação do artigo seminal The logic of animal conflict, onde foi pro-posto o conceito de Estratégias Evolutivamente Estáveis. O objetivo desse estudó e realizar uma síntese dos conceitos de modelagem em ecologia baseada em teoria dos jogos, realizados a partir de Maynard Smith, com uma aborda-gem introdutória e interdisciplinar, partindo de ideias econômicas e avançando para temas mais aplicados como modelos que apontam para o fenômeno de seleção dependente da frequência. Palavras-chave: jogos evolutivos, seleção dependente da frequência, estratégias mistas, equação do replicador
The abundance of Guiana dolphins (Sotalia guianensis) in Guanabara Bay, Rio de Janeiro, Southeast... more The abundance of Guiana dolphins (Sotalia guianensis) in Guanabara Bay, Rio de Janeiro, Southeastern Brazil, was investigated during the period 2000–2015 using mark-recapture models applied to photo-identification data. A combination of Pradel's model and Pollock's robust design was applied to estimate abundance and other population parameters, such as apparent survival (), capture probability (p) and seniority probability (). Total population size was estimated by correcting the estimates derived from the Pradel robust design model for the proportion of marked individuals in the population. The corrected abundance estimates decreased drastically (37%) between 2000 (62, 95% CI 59–65) and 2015 (39, 95% CI 37–40), and can be explained by a combination of low survival and recruitment rates. Determining the ultimate causes for the decline in this Guiana dolphin population is difficult, but the likely reasons are of anthropogenic nature, such as by-catch, habitat degradation, intense traffic of vessels and exposure to immunosuppressive and endocrine-disrupting pollutants. We provide the first quantitative evidence of population decline in a delphinid from Brazilian waters. Conservation and management actions are urged to change this scenario. Other local dolphin populations in Brazil, which are exposed to the same impacts, may also be currently declining or are expected to do so in the near future. For this reason, we emphasize that anthropogenic impacts upon estuarine/coastal species that exhibit site fidelity warrant greater attention, because such impacts may lead to the same negative scenario observed in Guanabara Bay.
We study the population size time series of a Neotropical small mammal with the intent of detecti... more We study the population size time series of a Neotropical small mammal with the intent of detecting and modelling population regulation processes generated by density-dependent factors and their possible delayed effects. The application of analysis tools based on principles of statistical generality are nowadays a common practice for describing these phenomena, but, in general, they are more capable of generating clear diagnosis rather than granting valuable modelling. For this reason, in our approach, we detect the principal temporal structures on the bases of different correlation measures, and from these results we build an ad-hoc minimalist autoregressive model that incorporates the main drivers of the dynamics. Surprisingly our model is capable of reproducing very well the time patterns of the empirical series and, for the first time, clearly outlines the importance of the time of attaining sexual maturity as a central temporal scale for the dynamics of this species. In fact, an important advantage of this analysis scheme is that all the model parameters are directly biologically interpretable and potentially measurable, allowing a consistency check between model outputs and independent measurements. One of the main objectives in the field of population dynamics is to determine the extent of deterministic vs. stochastic forces in time series of abundance and population parameters. The deterministic share of the observed fluctuations is usually assigned to nonlinear density-dependent processes, which create regulatory and stabilising forces 1. Different theoretical and modelling frameworks have been used through the history of population dynamics , but time series analysis and autoregressive models are a frequent and natural choice, as the population size in the future is related to the population size in the past 2–4. A variety of time series analysis methods have been used in population dynamics to diagnose their structure and density dependence 5 , particularly successful in the analysis of empirical data of long lived taxa such as mammals 6–8. The approach proposed by Royama 9 combines diagnostic tools with the use of phenomenological models, and has increased the predictive power and understanding of the dynamics of intensively studied systems 10–12. In general, for sufficiently long time series, it is possible to use conventional autoregressive models or to apply other analogous methods which aim to determine a clear differentiation between deterministic and random components 13,14. The most common approach 9,15 uses a linear autoregressive model of order k , which relates the logarithm of the population abundance (y t) at different time steps: ∑ β β ε = + +. () = −
This article is a review of the developmental trajectory of the scientific reasoning on populatio... more This article is a review of the developmental trajectory of the scientific reasoning on population biology in small mammal studies led by Prof. Rui Cerqueira throughout his career. The multidisciplinarity joining ecology, demography, genetics, epidemiology, biogeography, taxonomy and systematics, and the different approaches guided by relevant ecological questions have always been present in his research projects which led to the progress of the knowledge described here. We report three empirical studies of long-term population biology: the study in Restinga de Barra de Marica, RJ, a pioneer study in many aspects at the time; the study in Sumidouro, RJ, developed in collaboration with the Fundação Oswaldo Cruz, RJ, related to the role of wild rodents in the transmission dynamics of schistosomiasis; and the study in Garrafão, municipality of Guapimirim, RJ. The latter arose from ideas generated in the study of Restinga de Barra de Marica on movements and population structure of some marsupial species and is still in progress, being one of the longest population dynamics studies of small mammals in Brazil. New and important results were obtained in these three projects using the capture-mark-recapture technique that permitted to obtain high quality data. The contribution of Prof. Cerqueira raised the field of mammalogy and in particular the population biology of small mammals in Brazil to a level of international excellence, both in terms of generating new knowledge and training human resources, as well as in terms of progress and sophistication of methodologies and analyses. (OBS: The article was published in portuguese)
Estimates of local population abundances, which require carefully designed sampling procedures, c... more Estimates of local population abundances, which require carefully designed sampling procedures, can provide valuable information on population size and density. Even though small mammals are one of the most widely studied vertebrate groups, many surveys have not recorded basic information to estimate local abundances, for instance catching effort. Here we suggest a simple comparative trapping frequency index that can be used as an alternative to the relative abundance index in data sets that only contain the number of species and individuals collected, thus lacking information on sampling effort. To compare trapping frequency and relative abundances we used capture records from more than four years, from seven species of rodents and two marsupial species collected by the Brazilian Plague Service. We calculated the trapping frequency index of each species as the proportion of trapped individuals per total of all individuals caught. We found that this trapping index was significantly correlated with a relative abundance index (number of captured individuals divided by number of trap nights). Our findings suggest that the proposed index may be useful for comparisons in situations where data on catching effort is lacking. The index may also provide a simple, though approximate quantification of relative local abundances, with possible applications in comparative studies (e.g. meta-analysis). We suggest that this index is used in studies that do not focus on obtaining accurate population parameter estimates, but which nonetheless contain data that can still offer a representative measure to compare local population abundances.
Effects of density dependence on animal movements have received much attention in ecology, but it... more Effects of density dependence on animal movements have received much attention in ecology, but it is still debated to what extent dispersal and movements in general are density dependent, and their potential contribution to population regulation processes. Here, we determine the occurrence and nature of density dependence in the movements of a Neotropical marsupial, the black-eared opossum Didelphis aurita Wied-Neuwied 1826. Using spool-and-line tracking devices, we estimated the tortuosity of fine-scale movements of 149 individuals by their fractal dimension D.We evaluated the relative importance of population size, reproductive or climatic seasons and reproductive maturity of individuals as determinants of movement tortuosity, using a model selection approach. Population size was the most important determinant of movement tortuosity, with season (climatic seasons for females, reproductive seasons for males) and reproductive maturity as secondary but also important variables.We detected a positive density-dependent effect on movement tortuosity, resulting in more intensive use of areas by individuals during periods of high population size. This positive association between movement tortuosity and population size is more likely to result from intraspecific competition, which forces individuals to explore their environment more intensively during high-density periods. Therefore, despite being density dependent, movements in D. aurita apparently do not contribute to population regulation mechanisms.
Population fluctuations are the result of the combined action of endogenous (feedback structure) ... more Population fluctuations are the result of the combined action of endogenous (feedback structure) and exogenous factors (large- and local-scale climate variables). In this paper, we used a 13-year time series to identify the feedback structure in a population of the brown 4-eyed opossum Metachirus nudicaudatus and to test a hypothesis on the effects of El Niño Southern Oscillation and rainfall using Royama’s theoretical framework. Metachirus nudicaudatus was regulated by a strong 1st-order negative feedback, with intraspecific competition for food resources as the probable factor governing the endogenous system. Contrary to our expectations, El Niño did not explain the marsupial dynamics better than 1-year lagged rainfall, that may operate in 2 different manners: as a nonlinear perturbation effect influencing the strength of density dependence (intraspecific competition and intraguild predation) or as a lateral perturbation effect influencing the carrying capacity of the environment.
The relative effect of survival and reproductive rates to population growth rate is e... more The relative effect of survival and reproductive rates to population growth rate is expected to be similar across species with similar life-histories. We employed a matrix population model and sensitivity and elasticity analysis to assess the absolute and relative importance of age-specific survival and fertility to population growth rate of Didelphis aurita (Didelphimorphia, Didelphidae) in a rural area of Rio de Janeiro, southeastern Brazil. The results were compared to expectations for mammals that mature early and have short generation time, such as D. aurita. Prospective analysis showed that changes in pouch young and juveniles survival would have large effects on population growth rate, relative to other vital rates, being the most critical time periods in the life cycle of D. aurita, whereas the effect of fertilities were always low. These findings do not fit to the observed pattern in mammals that mature early, where reproductive parameters have the largest relative influence on population growth rate. Although reproductive rates were characterized by a relatively small influence on population growth rate, they are still relevant because of their high variability and response to potential environmental disturbances. The first application of matrix population models to a neotropical rainforest marsupial provides information on marsupial demography and life-history strategy, increasing comprehension of this unknown group.
Studies on habitat selection based on the presence and absence of individuals still rarely includ... more Studies on habitat selection based on the presence and absence of individuals still rarely include the uncertainty of absence. With it, one can model the probability of detec- tion, which is a parameter of interest especially when dealing with species where non-detection is common. Here, we per- formed an analysis of microhabitat selection of a New World marsupial (Marmosa paraguayana, Tate 1931)—an arboreal species endemic to the Brazilian Atlantic forest—accounting for false absence. We found empirical evidence supporting one of our hypotheses: the angle of the terrain’s inclination at a site positively affects detection probability. This is probably due to the fact that, at an inclined site, the area available to the animals tends to be larger and the proba- bility of detection of M. paraguayana would be higher, due either to greater local abundance or increased frequency of moving. The probability of resource use was heteroge- neous, or rather, not constant in space, but constant in time. We found weak evidence for the correlation between the canopy volume and the probability of resource use. However, we observed a tendency in the estimates of site-specific probability of resource use: the highest values of the probability of resource use appeared in the upper part of the study grid, where the canopies were denser as well as more closed. Thus, this specie’s prob- ability of resource use possibly diminishes in habitats such as early secondary forest with tiny canopies.
A fundamental step in the emerging Movement Theory is the description of movement paths, and the ... more A fundamental step in the emerging Movement Theory is the description of movement paths, and the identification of its proximate and ultimate drivers. The most common characteristic used to describe and analyze movement paths is its tortuosity, and a variety of tortuosity indices have been proposed in different theoretical or empirical contexts. Here we review conceptual differences between five movement indices and their bias due to loca- tions errors, sample sizes and scale-dependency: Intensity of Habitat use (IU), Fractal D, MSD (Mean Squared Distance), Straightness (ST), and Sinuosity (SI). Intensity of Habitat use and ST are straightforward to compute, but ST is actually an unbiased estimator of oriented search and ballistic movements. Fractal D is less straightforward to compute and repre- sents an index of propensity to cover the plane, whereas IU is the only completely empirical of the three. These three indices could be used to identify different phases of path, and their path tortuosity is a dimensionless feature of the path, depending mostly on path shape, not on the unit of measurement. This concept of tortuosity differs from a concept implied in the sinuosity of BENHAMOU (2004), where a specific random walk movement model is assumed, and diffusion distance is a function of path length and turning angles, requiring their inclusion in a measure of sinuosity. MSD should be used as a diagnostic tool of random walk paths rather than an index of tortuosity. Bias due to location errors, sample size and scale, differs between the indices, as well as the concept of tortuosity implied. These differences must be considered when choosing the most appropriate index.
A population of the black-eared opossum, Didelphis aurita Wied-Neuwied 1826, was studied during 1... more A population of the black-eared opossum, Didelphis aurita Wied-Neuwied 1826, was studied during 1997-2006 by capture-mark-recapture in the Atlantic Forest in the state of Rio de Janeiro. Cohorts were established with females marked still in the pouch, classified into five age classes. Population parameters were estimated using life tables. Survival was type III and mortality was greatest in age classes I and II, just after weaning. Fecundity was inversely correlated with survival, reproductive value was inversely correlated with mortality and residual reproductive value was inversely correlated with fecundity. The intrinsic rate of increase was always close to zero and tended to be slightly negative. The black-eared opossum can be considered a good model species for this type of study.
A major difficulty in the application of probabilistic models to estimations of mammal abundance ... more A major difficulty in the application of probabilistic models to estimations of mammal abundance is obtaining a data set that meets all of the assumptions of the model. In this paper, we evaluated the concordance correlation among three population size estimators, the minimum number alive (MNA), jackknife and the model suggested by the selection algorithm in CAPTURE (the best-fit model), using long-term data on three Brazilian small mammal species obtained from three different studies. The concordance correlation coefficients between the abundance estimates indicated that the probabilistic and enumeration estimators were highly correlated, giving concordant population estimates, except for one species in one of the studies. The results indicate the adequacy of using enumeration estimates as indexes for population size when scarce data do not allow for the use of probabilistic methods. Differences observed in the behavior of enumera- tion and probabilistic methods among species and studies can be related to the exclusive sampling design of each area, species-specific movement characteristics and whether a significant portion of the population could be sampled.
The genetics and ecology of pumas are well documented in North America but there is a lack of stu... more The genetics and ecology of pumas are well documented in North America but there is a lack of studies in South America, especially in Brazil. By means of a noninvasive method, faecal DNA analysis, we estimated puma abundance in two protected areas embedded in a human-disturbed landscape in the north-east of São Paulo state, in south-east Brazil. In 8 months of mark–recapture faeces sampling, 15 individual pumas were identified using seven microsatellite loci. The estimated abundance of pumas with the Jolly–Seber open population model was 23.81 ± SE 6.22. This is the first estimate of the abundance of pumas in a human-dominated landscape in São Paulo state, the most populous, developed and industrialized state of Brazil. The absence of high-quality habitats in the north- east of the state, the absence of direct competitors and the high availability of prey in protected areas are probably contributing to the high number of pumas concentrated in a relatively small area (c. 260 km2). Our results will contribute to the long-term monitoring of this puma population and, combined with other ecological, behaviour- al and genetic data, will help guide conservation action to maintain a viable population of the puma in this region.
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Papers by Maja Kajin
The multidisciplinarity joining ecology, demography, genetics, epidemiology, biogeography,
taxonomy and systematics, and the different approaches guided by relevant ecological questions have always been present in his research projects which led to the progress of the knowledge described here. We report three empirical studies of long-term population biology: the study in Restinga de Barra de Marica, RJ, a pioneer study in many aspects at the time; the study in Sumidouro, RJ, developed in collaboration with the Fundação Oswaldo Cruz, RJ, related to the role of wild rodents in the transmission dynamics of schistosomiasis; and the study in
Garrafão, municipality of Guapimirim, RJ. The latter arose from ideas generated in the study of Restinga de Barra de Marica on movements and population structure of some marsupial
species and is still in progress, being one of the longest population dynamics studies of small
mammals in Brazil. New and important results were obtained in these three projects using the capture-mark-recapture technique that permitted to obtain high quality data. The contribution of Prof. Cerqueira raised the field of mammalogy and in particular the population biology of
small mammals in Brazil to a level of international excellence, both in terms of generating new knowledge and training human resources, as well as in terms of progress and sophistication of methodologies and analyses. (OBS: The article was published in portuguese)
still debated to what extent dispersal and movements in general are density dependent, and their potential
contribution to population regulation processes. Here, we determine the occurrence and nature of density dependence
in the movements of a Neotropical marsupial, the black-eared opossum Didelphis aurita Wied-Neuwied 1826.
Using spool-and-line tracking devices, we estimated the tortuosity of fine-scale movements of 149 individuals by
their fractal dimension D.We evaluated the relative importance of population size, reproductive or climatic seasons
and reproductive maturity of individuals as determinants of movement tortuosity, using a model selection
approach. Population size was the most important determinant of movement tortuosity, with season (climatic
seasons for females, reproductive seasons for males) and reproductive maturity as secondary but also important
variables.We detected a positive density-dependent effect on movement tortuosity, resulting in more intensive use
of areas by individuals during periods of high population size. This positive association between movement
tortuosity and population size is more likely to result from intraspecific competition, which forces individuals to
explore their environment more intensively during high-density periods. Therefore, despite being density dependent,
movements in D. aurita apparently do not contribute to population regulation mechanisms.
The multidisciplinarity joining ecology, demography, genetics, epidemiology, biogeography,
taxonomy and systematics, and the different approaches guided by relevant ecological questions have always been present in his research projects which led to the progress of the knowledge described here. We report three empirical studies of long-term population biology: the study in Restinga de Barra de Marica, RJ, a pioneer study in many aspects at the time; the study in Sumidouro, RJ, developed in collaboration with the Fundação Oswaldo Cruz, RJ, related to the role of wild rodents in the transmission dynamics of schistosomiasis; and the study in
Garrafão, municipality of Guapimirim, RJ. The latter arose from ideas generated in the study of Restinga de Barra de Marica on movements and population structure of some marsupial
species and is still in progress, being one of the longest population dynamics studies of small
mammals in Brazil. New and important results were obtained in these three projects using the capture-mark-recapture technique that permitted to obtain high quality data. The contribution of Prof. Cerqueira raised the field of mammalogy and in particular the population biology of
small mammals in Brazil to a level of international excellence, both in terms of generating new knowledge and training human resources, as well as in terms of progress and sophistication of methodologies and analyses. (OBS: The article was published in portuguese)
still debated to what extent dispersal and movements in general are density dependent, and their potential
contribution to population regulation processes. Here, we determine the occurrence and nature of density dependence
in the movements of a Neotropical marsupial, the black-eared opossum Didelphis aurita Wied-Neuwied 1826.
Using spool-and-line tracking devices, we estimated the tortuosity of fine-scale movements of 149 individuals by
their fractal dimension D.We evaluated the relative importance of population size, reproductive or climatic seasons
and reproductive maturity of individuals as determinants of movement tortuosity, using a model selection
approach. Population size was the most important determinant of movement tortuosity, with season (climatic
seasons for females, reproductive seasons for males) and reproductive maturity as secondary but also important
variables.We detected a positive density-dependent effect on movement tortuosity, resulting in more intensive use
of areas by individuals during periods of high population size. This positive association between movement
tortuosity and population size is more likely to result from intraspecific competition, which forces individuals to
explore their environment more intensively during high-density periods. Therefore, despite being density dependent,
movements in D. aurita apparently do not contribute to population regulation mechanisms.