The effect of different variables on the territory size and defence level of tawny owl (Strix alu... more The effect of different variables on the territory size and defence level of tawny owl (Strix aluco L.) populations was studied in two habitats: mixed farmland (1976–1978) and town (1986–1988). Territory size was determined by plotting the position of territorial challenges (hoots) of males which were individually recognizable in most cases. No differences were found in size, defence, number of competitors and biomass between territories in farmland and in town, but territories in town were more fragmented and showed a larger nearest neighbour distance. Size of rural territories was adequately predicted both by some structural habitat features and food supplies, while size of urban territories was affected only by habitat structure and by years of territory occupancy. No effect on territory size by competing neighbours was found in either habitat, thus confirming that behavioural interactions between the owners of territories and potential settlers prevent a decrease of territory size.Defence level of urban territories was affected by 'social’variables (nearest neighbour distance and years of occupancy), structural variables (percentage of poplar grove and diversity), and food supply, while in rural territories only structural variables (fragmentation or natural vegetation) and food supplies affected defence level.This was due to different settlement tactics in the two areas, depending on the extent and quality of suitable habitat.
ABSTRACT The responses of male and female Long-eared Owls to a human approaching the nest were ex... more ABSTRACT The responses of male and female Long-eared Owls to a human approaching the nest were examined. Each nest was only tested once. Nest defence increased significantly throughout the breeding season because older chicks were defended more strongly than younger chicks and eggs. No correlations were however found between defence intensity and laying date, clutch- or brood-size. These results generally do not support either the renesting-potential hypothesis or the positive reinforcement hypothesis but are in accordance with both the age-investment hypothesis and the vulnerability hypothesis. Females defended nestlings more often and more vigorously than did males. Given division of labour between sexes and the related reversed sexual dimorphism in size, female Long-eared Owls may be more willing to engage in nest defence simply because they are always nearer eggs and chicks during all breeding stages and are larger/heavier than males; consequently they may allocate more time and energy to this activity. Finally, owls experiencing higher levels of human persecution took smaller risks when defending nests than owls breeding in an undisturbed area.
At Anzali Lagoon, on the southwest coast of the Caspian Sea, Great Crested Grebes Podiceps crista... more At Anzali Lagoon, on the southwest coast of the Caspian Sea, Great Crested Grebes Podiceps cristatus were observed breeding both in monospecific colonies and in a mixed colony with Whiskered Terns Chlidonias hybridus. In the mixed colony, Great Crested Grebes bred later than in their monospecific colonies, while laying clutches of similar size, but significantly fewer of their nests disappeared during incubation and their chicks had higher survival rates up to at least 20 days old. Human disturbance and the resulting increases in predation likely caused greater losses at monospecific colonies of Great Crested Grebes where there is no common anti-predatory activity; while the strong anti-predatory behaviour of Whiskered Terns in the mixed colony might have offered enhanced protection to the chicks. Unfortunately, we could not separate the effects of the seasonal differences in human disturbance and of the protective presence of terns on the Great Crested Grebe's reproductive output.
... 16 P. NINNI,4 M. PETRIE,17 F. PULIDO,18 D. RUBOLINI,9 N. SAINO,19 JJ SOLER,3 M. SOLER,15 C. S... more ... 16 P. NINNI,4 M. PETRIE,17 F. PULIDO,18 D. RUBOLINI,9 N. SAINO,19 JJ SOLER,3 M. SOLER,15 C. SPOTTISWOODE,20 T. SZÉP,21 R. THORNHILL,22 C. ZAMORA,15 ROBERTO ... A, 5ème étage, case courrier 29, 7 Quai Saint Bernard, 75252 Paris Cedex 05, France. ...
... 16 P. NINNI,4 M. PETRIE,17 F. PULIDO,18 D. RUBOLINI,9 N. SAINO,19 JJ SOLER,3 M. SOLER,15 C. S... more ... 16 P. NINNI,4 M. PETRIE,17 F. PULIDO,18 D. RUBOLINI,9 N. SAINO,19 JJ SOLER,3 M. SOLER,15 C. SPOTTISWOODE,20 T. SZÉP,21 R. THORNHILL,22 C. ZAMORA,15 ROBERTO ... A, 5ème étage, case courrier 29, 7 Quai Saint Bernard, 75252 Paris Cedex 05, France. ...
We tested 11 male Scops Owls (Otus scops) and their mates with the playback of conspecific male a... more We tested 11 male Scops Owls (Otus scops) and their mates with the playback of conspecific male and female calls to determine whether their response to intruders differed according to the sex of the intruder. Eight measures of response intensity were recorded for each owl. Territorial defense appeared to be strictly cooperative with both members of a pair reacting to intruders of either sex. Males responded more strongly to male playbacks for five measures of response intensity indicating that males are more aggressive toward intruding males. Females also showed a tendency to respond stronger to female playbacks, but, overall, both sexes showed little reaction to female calls. This may provide a mechanism for polygyny in this species. K¾ WOtDS: Otus scops, Scs Owl, cooperative nest defense, intrasexual aggression, territory defense.
The presence of predators can induce changes in both the morphology and behaviour of Anuran larva... more The presence of predators can induce changes in both the morphology and behaviour of Anuran larvae, affecting both their size and developmental stage at metamorphosis and, consequently, the fitness of adult individuals. Tadpoles have been shown to be capable of finely tuning their defensive responses according to the actual risk perceived, which is expected to vary according to the prey-to-predator size ratio. In this study, we exposed common frog (Rana temporaria) tadpoles (Gosner stages 28–30), for a period of 2 weeks, to the non-lethal presence of dragonfly larvae (Anax imperator) and backswimmers (Notonecta glauca). In such a narrow window of time, we expected behavioural responses to be similar for both predators and exposure to predation risk to have negligible effects on tadpole development and weight. Overall, tadpoles increased hiding behaviour and were less active when predators were present in the experimental mesocosms, but behavioural responses were constrained to the early phase of the ontogeny and were no longer used when tadpoles reached a threshold size. Developmental rate slightly slowed down for predator treatments in comparison to controls, possibly as a consequence of energetic investment in unrecorded morphological defences. Although variation in laboratory conditions and protocols makes it hard to compare the results of different experiments, our results contribute to verify the consistency of behavioural responses in Anuran larvae.
Neurophysiological modifications associated to phenotypic plasticity in response to predators are... more Neurophysiological modifications associated to phenotypic plasticity in response to predators are largely unexplored, and there is a gap of knowledge on how the information encoded in predator cues is processed by prey sensory systems. To explore these issues, we exposed Rana dalmatina embryos to dragonfly chemical cues (kairomones) up to hatching. At different times after hatching (up to 40 days), we recorded morphology and antipredator behaviour of control and embryonic-treated tadpoles as well as their neural olfactory responses, by recording the activity of their mitral neurons before and after exposure to a kairomone solution. Embryonic-treated embryos hatched later and originated smaller hatchlings than control siblings. In addition, embryonic-treated tadpoles showed a stronger antipredator response than controls at 10 (but not at 30) days post-hatching, though the intensity of the contextual response to the kairomone stimulus did not differ between the two groups. Baseline ne...
The effect of different variables on the territory size and defence level of tawny owl (Strix alu... more The effect of different variables on the territory size and defence level of tawny owl (Strix aluco L.) populations was studied in two habitats: mixed farmland (1976–1978) and town (1986–1988). Territory size was determined by plotting the position of territorial challenges (hoots) of males which were individually recognizable in most cases. No differences were found in size, defence, number of competitors and biomass between territories in farmland and in town, but territories in town were more fragmented and showed a larger nearest neighbour distance. Size of rural territories was adequately predicted both by some structural habitat features and food supplies, while size of urban territories was affected only by habitat structure and by years of territory occupancy. No effect on territory size by competing neighbours was found in either habitat, thus confirming that behavioural interactions between the owners of territories and potential settlers prevent a decrease of territory size.Defence level of urban territories was affected by 'social’variables (nearest neighbour distance and years of occupancy), structural variables (percentage of poplar grove and diversity), and food supply, while in rural territories only structural variables (fragmentation or natural vegetation) and food supplies affected defence level.This was due to different settlement tactics in the two areas, depending on the extent and quality of suitable habitat.
ABSTRACT The responses of male and female Long-eared Owls to a human approaching the nest were ex... more ABSTRACT The responses of male and female Long-eared Owls to a human approaching the nest were examined. Each nest was only tested once. Nest defence increased significantly throughout the breeding season because older chicks were defended more strongly than younger chicks and eggs. No correlations were however found between defence intensity and laying date, clutch- or brood-size. These results generally do not support either the renesting-potential hypothesis or the positive reinforcement hypothesis but are in accordance with both the age-investment hypothesis and the vulnerability hypothesis. Females defended nestlings more often and more vigorously than did males. Given division of labour between sexes and the related reversed sexual dimorphism in size, female Long-eared Owls may be more willing to engage in nest defence simply because they are always nearer eggs and chicks during all breeding stages and are larger/heavier than males; consequently they may allocate more time and energy to this activity. Finally, owls experiencing higher levels of human persecution took smaller risks when defending nests than owls breeding in an undisturbed area.
At Anzali Lagoon, on the southwest coast of the Caspian Sea, Great Crested Grebes Podiceps crista... more At Anzali Lagoon, on the southwest coast of the Caspian Sea, Great Crested Grebes Podiceps cristatus were observed breeding both in monospecific colonies and in a mixed colony with Whiskered Terns Chlidonias hybridus. In the mixed colony, Great Crested Grebes bred later than in their monospecific colonies, while laying clutches of similar size, but significantly fewer of their nests disappeared during incubation and their chicks had higher survival rates up to at least 20 days old. Human disturbance and the resulting increases in predation likely caused greater losses at monospecific colonies of Great Crested Grebes where there is no common anti-predatory activity; while the strong anti-predatory behaviour of Whiskered Terns in the mixed colony might have offered enhanced protection to the chicks. Unfortunately, we could not separate the effects of the seasonal differences in human disturbance and of the protective presence of terns on the Great Crested Grebe's reproductive output.
... 16 P. NINNI,4 M. PETRIE,17 F. PULIDO,18 D. RUBOLINI,9 N. SAINO,19 JJ SOLER,3 M. SOLER,15 C. S... more ... 16 P. NINNI,4 M. PETRIE,17 F. PULIDO,18 D. RUBOLINI,9 N. SAINO,19 JJ SOLER,3 M. SOLER,15 C. SPOTTISWOODE,20 T. SZÉP,21 R. THORNHILL,22 C. ZAMORA,15 ROBERTO ... A, 5ème étage, case courrier 29, 7 Quai Saint Bernard, 75252 Paris Cedex 05, France. ...
... 16 P. NINNI,4 M. PETRIE,17 F. PULIDO,18 D. RUBOLINI,9 N. SAINO,19 JJ SOLER,3 M. SOLER,15 C. S... more ... 16 P. NINNI,4 M. PETRIE,17 F. PULIDO,18 D. RUBOLINI,9 N. SAINO,19 JJ SOLER,3 M. SOLER,15 C. SPOTTISWOODE,20 T. SZÉP,21 R. THORNHILL,22 C. ZAMORA,15 ROBERTO ... A, 5ème étage, case courrier 29, 7 Quai Saint Bernard, 75252 Paris Cedex 05, France. ...
We tested 11 male Scops Owls (Otus scops) and their mates with the playback of conspecific male a... more We tested 11 male Scops Owls (Otus scops) and their mates with the playback of conspecific male and female calls to determine whether their response to intruders differed according to the sex of the intruder. Eight measures of response intensity were recorded for each owl. Territorial defense appeared to be strictly cooperative with both members of a pair reacting to intruders of either sex. Males responded more strongly to male playbacks for five measures of response intensity indicating that males are more aggressive toward intruding males. Females also showed a tendency to respond stronger to female playbacks, but, overall, both sexes showed little reaction to female calls. This may provide a mechanism for polygyny in this species. K¾ WOtDS: Otus scops, Scs Owl, cooperative nest defense, intrasexual aggression, territory defense.
The presence of predators can induce changes in both the morphology and behaviour of Anuran larva... more The presence of predators can induce changes in both the morphology and behaviour of Anuran larvae, affecting both their size and developmental stage at metamorphosis and, consequently, the fitness of adult individuals. Tadpoles have been shown to be capable of finely tuning their defensive responses according to the actual risk perceived, which is expected to vary according to the prey-to-predator size ratio. In this study, we exposed common frog (Rana temporaria) tadpoles (Gosner stages 28–30), for a period of 2 weeks, to the non-lethal presence of dragonfly larvae (Anax imperator) and backswimmers (Notonecta glauca). In such a narrow window of time, we expected behavioural responses to be similar for both predators and exposure to predation risk to have negligible effects on tadpole development and weight. Overall, tadpoles increased hiding behaviour and were less active when predators were present in the experimental mesocosms, but behavioural responses were constrained to the early phase of the ontogeny and were no longer used when tadpoles reached a threshold size. Developmental rate slightly slowed down for predator treatments in comparison to controls, possibly as a consequence of energetic investment in unrecorded morphological defences. Although variation in laboratory conditions and protocols makes it hard to compare the results of different experiments, our results contribute to verify the consistency of behavioural responses in Anuran larvae.
Neurophysiological modifications associated to phenotypic plasticity in response to predators are... more Neurophysiological modifications associated to phenotypic plasticity in response to predators are largely unexplored, and there is a gap of knowledge on how the information encoded in predator cues is processed by prey sensory systems. To explore these issues, we exposed Rana dalmatina embryos to dragonfly chemical cues (kairomones) up to hatching. At different times after hatching (up to 40 days), we recorded morphology and antipredator behaviour of control and embryonic-treated tadpoles as well as their neural olfactory responses, by recording the activity of their mitral neurons before and after exposure to a kairomone solution. Embryonic-treated embryos hatched later and originated smaller hatchlings than control siblings. In addition, embryonic-treated tadpoles showed a stronger antipredator response than controls at 10 (but not at 30) days post-hatching, though the intensity of the contextual response to the kairomone stimulus did not differ between the two groups. Baseline ne...
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