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Large initial body size and rapid early growth rate are important in many species, both because predation rates decline as individuals grow and because females that attain a larger adult body size are more fecund. To identify possible factors contributing to size and growth rate variation in hatchling green iguanas, we artificially incubated six clutches at three constant temperatures to test for effects of incubation temperature and/or clutch effects on initial size and growth rate. Higher incubation temperatures resulted in significantly shorter incubation periods but did not influence initial body size. There were significant differences among clutches in egg size, and also in initial hatchling body size, even after correcting for differences in egg size among clutches. A subset of hatchlings from each nest was reared in semi-natural conditions for four months, with individuals from the high incubation temperature condition exhibiting the slowest longer-term growth rates. No clutch effects were detected in the growth rate analyses. The observed variation in early growth rate of juvenile iguanas seems to be selectively important and this variation may be due in part to the conditions the eggs experience during incubation, but clutch effects in this study were limited to egg size and initial hatchling body size variation, but were not found for subsequent growth rates.

Few studies have been conducted on the population dynamics of crocodiles, especially in the Neotropics. This is the first study to provide data on the population dynamics of the threatened American crocodile (Crocodylus acutus (Cuvier, 1807)) in Paramillo National Natural Park. Twenty-four survey routes of 22km each were studied, and a total of 733 sightings was recorded. During the study period (from October 2014 to March 2016), the population remained stable and experienced slight growth (λ=1.049±0.428). Offspring production by the adults II stage was the most sensitive contribution (17.05), whereas the permanence of this adult stage was the demographic process that contributed the most to population growth (0.653). However, an 18% decrease in adults II would jeopardise long-term population viability and lead to a high probability of quasi-extinction, with under 300 individuals over the next 30 years. Thus, despite the apparent stability of this population, we suggest that it be considered a key target for future conservation efforts. Additionally, we recommend that this species continue to be listed as endangered in Colombia and not be modified in the CITES Appendix I.

ResumenSe determinó la ecología trófica de la lagartija Xenosaurus mendozai en Querétaro, México, identificando la importancia relativa de las presas consumidas y evaluando las diferencias intersexuales en la composición de la dieta, a lo largo de un año. Para ello, se calculó su valor de importancia (IX), se evaluó el nivel de especialización mediante el índice de Levins, así como el solapamiento mediante el índice de Pianka. Los análisis del contenido del tracto digestivo indican que son insectívoras y su dieta se basa principalmente en 12 órdenes, de los cuales las larvas de lepidópteros, los coleópteros y los ortópteros representan más del 60% de su dieta; por lo que la tendencia de esta población es hacia la especialización (BA=0.015), con un alto índice de solapamiento entre machos y hembras (OMH=0.946). En términos generales, la conformación de la dieta de esta especie es similar a lo registrado en otras especies del género, lo que puede estar determinado por el uso del microhábitat. Sin embargo, se requiere de estudio de disponibilidad de presas para describir con mayor precisión las preferencias alimentarias, así como para realizar pruebas experimentales que permitan determinar si existe preferencia por algún tipo particular de presas.AbstractThe feeding ecology of the knob-scaled lizard Xenosaurus mendozai from Querétaro, México, was studied in order to identify the relative importance of prey consumed, by evaluating the intersexual differences in the composition of their diet, throughout a year. Therefore, we calculated the importance value (IX) of each item, the trophic breadth by the standardized index of Levins’, and the dietary niche overlap using the Pianka's index. Our results indicate that these lizards are insectivorous and their diet is mainly based in at least 12 orders, of which Lepidoptera larvae, Coleoptera and Orthoptera represent over 60% of their diets; so the tendency of this population is towards specialization (BA=0.015), with a high overlap index between males and females (OMF=0.946). In general the diet of this species is similar to those reported in other species of the genus, which can be strongly influenced by microhabitat use. However, additional studies of prey availability are necessary to accurately describe food preferences, and experimental tests to determe whether there is a preference for a particular type of prey.

Flight initiation distance is defined as the distance between a prey and an approaching predator when the prey starts to flee. Escape theory predicts that the optimal flight initiation distance is the distance where predation risk rises to the point at which it equals the cost of fleeing. Therefore, staying close to refuge and occupying microhabitats with more abundant shelters (i.e., crevices or shrubs) may allow lizards to have shorter flight initiation distance. By simulating an approaching predator, we studied the effect of microhabitat structural complexity on escape behaviour, in particular, the distance fled before stopping and final distance (predator-prey distance when the prey stops fleeing), of a small diurnal tropical gecko, the yellow-headed geckoGonatodes albogularisinhabiting a tropical dry forest. The findings indicate that refuge abundance and distance to the nearest potential refuge influence escape behaviour ofG. albogularis. In addition, we found sex differences in escape behaviour which are not explained by microhabitat use. Females had longer flight initiation distance but shorter distance fled, and longer final distances than males.

The evolution of ecological and morphological traits to attract seed dispersal animals is common in many plant species. However, these traits can also attract seed predators. These selection pressures stimulate the generation of strategies to attract more dispersers than predators. Here, we describe a strategy used by the Astrocaryum malybo palm to avoid predation of unripe fruits using prickles as a structural defense. We use camera traps to monitor three individuals of the palm for five months. We analyzed 83 videos of two animal species interacting with the palms fruits (Central American Agouti, Dasyprocta punctata and Red-tailed Squirrel, Notosciurus granatensis). Of these, six correspond to an individual with unprotected unripe fruits and 77 to an individual with exposed ripe fruits. No interaction was recorded in the individual with protected unripe fruits. We suggest that A. malybo has developed these prickles as a structural defense strategy to protect its unripe fruits from vertebrate predators. We use camera traps that allow documentation of basic natural history information including such otherwise cryptic interactions. This type of information can be used in models of food web structure, revealing unknown details of the ecological and evolutionary processes of such species interactions.