First insights on habitat use by the endemic Selvagens gecko (Tarentola boettgeri bischoffi)

The Selvagens gecko (Tarentola boettgeri bischoffi Joger, 1984) is a medium sized gecko endemic to the Sel-vagens archipelago, Madeira, Portugal. The biology of this gecko is poorly known and in this study we present the first evidence regarding its habitat use. In 2010 (spring and autumn) and 2011 (spring), we collected data on the characteristics of the habitat surrounding 168 rocks used by these geckos as retreat sites, as well as on 75 randomly selected rocks. We also recorded body measurements of the individuals caught under each rock. In both seasons retreat site occupancy was found to be related to rock area, with geckos being found mainly under large rocks. Interestingly, we found that in spring heavier males, in better body condition, occupied the largest rocks and larger geckos occupied rocks closer to creek beds. Our results shed some light upon the behavioural ecology of this nocturnally active ecto-therm, that spends the day under a retreat site: i) intraspecific competition may be an ecological factor prevalent in this species, since larger individuals occupy larger rocks, located in a presumably high quality micro-habitat; ii) the possibility of spring territoriality in males, that compete for good quality shelters.

Behavioural Processes

In small sedentary ectotherms, patterns of spatial use result from the interplay between multiple, often conflicting factors, including abiotic and biotic interactions. Evaluating the costs and benefits of these pressures is crucial to make correct behavioural decisions in terms of fitness. The insular São Vicente's wall gecko Tarentola substituta provides a relatively simple model system to study these questions as it inhabits arid rocky habitats where refuges are limited, density of conspecifics is high, and terrestrial predators are almost absent. In the field, adults tend to find diurnal shelter under mid-sized rocks, frequently in male-female couples, while juveniles occupy small rocks which are thermally suboptimal. A lab experiment was conducted to determine the roles of ecological (shelter size and temperature) and social (conspecifics) factors in refuge selection. Single and pair combinations of geckos of different age and sex classes were allowed to select among four refuges: cold small, hot small, cold large, or hot large rock. Based on previous studies, we hypothesized that larger and thermally buffered rocks would be the preferred refuges, and that adult male-female pairs under the same rock would be more frequent than other combinations.Geckos primarily selected larger shelters, trading off the presence of conspecifics against thermal quality. In social terms, sex, adult condition and size-related disparity shaped the patterns of aggregation, resulting in lower aggregation frequencies between adults and juveniles and even between juveniles of different sizes. These results reasonably match field observations suggesting selection of rocks as diurnal retreats according to their thermal properties, and social aggregations mainly involving adult males and females but not juveniles. Overall, this combined evidence provides insights on the spatial ecology of geckos, and likely other ectotherms, under conditions of low predation, limited resources and high intraspecific competition, such as those prevailing on island systems.

We describe the ecology of the gecko Gymnodactylus geckoides amarali in the Cerrado of central Brazil and using published data, compare it with the conspecific Gymnodactylus geckoides geckoides from the Caatinga of northeastern Brazil. Gymnodactylus geckoides amarali is rupicolous, living primarily in rock crevices in ‘‘campos rupestres’’ (rocky fields), which are highly patchy in Cerrado. Field body temperatures were low and associated with environmental temperatures, suggesting thermoconformity. Termites were the most important food item, and consumption was greatest during the dry season. We suggest that access to termites is facilitated by the shallow soils used by G. g. amarali and by its well-developed chemosensory apparatus. Reproduction was concentrated in the dry season, a pattern known for very few Cerrado squamates, possibly because of the higher availability of termites during that period. Clutch size was significantly correlated with female size, a pattern unknown in any other gecko, and there was no association between egg size and female size. Gymnodactylus geckoides amarali produced larger clutches of smaller eggs relative to G. g. geckoides, presumably because of the high climatic unpredictability of the Caatinga. We detected a significant sexual dimorphism in both body size and shape: females were larger and had smaller heads than males. We suggest that large female size is likely a plesiomorphic character of gekkonids and that large head size in males results from sexual selection theory.

2013

Journal of Herpetology, 2012

Journal of Zoology, 2007

We tested three non-exclusive hypotheses that the lizard, Gymnodactylus carvalhoi, lives in termitaria to avoid thermal extremes, to avoid predators, or because of an abundance of food (dietary specialist). We first confirm that these geckos are restricted to termitaria in the region studied. Body temperatures (T b ) of geckos averaged below environmental temperatures during day outside of termitaria and above outside temperatures at night; T b averaged only slightly higher than temperatures inside termitaria. We conclude that thermal constraints in Cerrado habitats lacking rocks restrict Gymnodactylus to termite nests. High frequencies of tail loss and the presence of many potential predators within termitaria suggest high encounter rates with predators, indicating that predation pressure does not restrict these geckos to termite nests. Dietary data indicate that G. carvalhoi is a termite specialist. Published data indicate that other Gymnodactylus species and populations are also termite specialists, even though several live primarily outside termitaria (in crevices and under rocks). An evolutionary history of termite specialization and low thermal requirements in the clade (Gymnodactylus) predispose them to feed on termites within the termitaria.

Israel Journal of Ecology and Evolution, 2019

Geckos are a hyper-diverse, ancient, and globally distributed group. They have diverged early from other squamates and thus can be expected to differ from them along multiple ecological, life history, and biogeographic axes. I review a wide range of gecko traits, comparing them to those of other lizard taxa, to identify the unique, and unifying, attributes of geckos among lizards, based on comprehensive databases of lizard distributions and biological attributes. Few traits completely separate geckos from other lizard taxa, yet they differ to a large degree along many axes: they are more restricted to low latitudes and altitudes, are especially diverse on islands, but relatively scarce in America. They are small lizards, that lay small, fixed clutch sizes, for which they compensate only partially by laying frequently. Because they mature at relatively similar ages and have similar lifespans to other lizards, geckos produce fewer offspring over a year, and over their lifetimes, perha...

Journal of …, 2007

We tested three non-exclusive hypotheses that the lizard, Gymnodactylus carvalhoi, lives in termitaria to avoid thermal extremes, to avoid predators, or because of an abundance of food (dietary specialist). We first confirm that these geckos are restricted to termitaria in the region studied. Body temperatures (T b ) of geckos averaged below environmental temperatures during day outside of termitaria and above outside temperatures at night; T b averaged only slightly higher than temperatures inside termitaria. We conclude that thermal constraints in Cerrado habitats lacking rocks restrict Gymnodactylus to termite nests. High frequencies of tail loss and the presence of many potential predators within termitaria suggest high encounter rates with predators, indicating that predation pressure does not restrict these geckos to termite nests. Dietary data indicate that G. carvalhoi is a termite specialist. Published data indicate that other Gymnodactylus species and populations are also termite specialists, even though several live primarily outside termitaria (in crevices and under rocks). An evolutionary history of termite specialization and low thermal requirements in the clade (Gymnodactylus) predispose them to feed on termites within the termitaria.

Amphibia-reptilia, 1988

Hemidactylus brookii was the most common gecko in the Terai of central Nepal, occurring both in the forest and on buildings. In the Royal Chitwan National Park, samples of adult males (46.4 ± 0.04 mm SVL) were not significantly different from adult females (45.3 + 0.04 mm SVL) in body size and head measurements, except head width (males 9.1 ± 0.2 mm, females 8.7 ± 0.1 mm). All measures of head size were significantly different between sexes when the effect of body size was removed. Males were sexually mature at 42 mm SVL and females at 43 mm SVL. The reproductive pattern of both species is vernal; activities are concentrated in spring (premonsoon). Growth averaged 0.8 mm/month between premonsoon and postmonsoon sampling periods. Adult survivorship was estimated at 14.3% for this six month period. Population size was estimated at 105 lizards on six small buildings in a < 1 ha area. Peak activity period was 1900-2300 h. Hemidactylus brookii in Nepal appears to possess life history characteristics associated with annual population turnover.

Journal of Herpetology, 2016

Microhabitat use is an important aspect of an organism's niche, often influencing both intra-and interspecific interactions such as competition. To reduce competitive interactions, species may shift their behavior when in sympatry to gain greater access to resources, resulting in patterns of habitat partitioning. Previous studies have described structural microhabitat partitioning in Phelsuma geckos with the likely cause being interference competition. Such interference competition also may lead to temporal microhabitat partitioning. We investigated the presence of temporal habitat partitioning in Phelsuma geckos from Mauritius and the relation of partitioning to competition. We found temporal variation in microhabitat use for Mauritian Phelsuma. However, this variation was not clearly associated with the presence of other focal Phelsuma species, suggesting competition may not be responsible for the observed pattern. Temporal habitat partitioning in Mauritian Phelsuma geckos may be attributable to historical competition or other factors such as thermoregulation, food availability, or predator avoidance. We encourage future studies to investigate the mechanisms of temporal microhabitat variation.