Unwrapping broken tails: Biological and environmental correlates of predation pressure in limbless reptiles.

Studying species interactions in nature often requires elaborated logistics and intense fieldwork. The difficulties in such task might hinder our ability to answer questions on how biotic interactions change with the environment. Fortunately, a workaround to this problem lies within scientific collections. For some animals, the inspection of preserved specimens can reveal the scars of past antagonistic encounters, such as predation attempts. A common defensive behaviour that leaves scars on animals is autotomy, the loss of a body appendage to escape predation. By knowing the collection site of preserved specimens, it is possible to assess the influence of organismal biology and the surrounding environment in the occurrence of autotomy. We gathered data on tail loss for 8189 preserved specimens of 33 snake and 11 amphisbaenian species to investigate biological and environmental correlates of autotomy in reptiles. We applied generalized linear mixed effect models to evaluate whether body size, sex, life-stage, habitat use, activity pattern, biome, tropicality, temperature and precipitation affect the probability of tail loss in limbless reptiles. We observed autotomy in 23.6% of examined specimens, with 18.7% of amphisbaenian and 33.4% of snake specimens showing tail loss. The probability of tail loss did not differ between snakes and amphisbaenians, but it was higher among large-sized specimens, particularly in adults and females. Chance of tail loss was higher for diurnal and arboreal species, and among specimens collected in warmer regions, but it was unaffected by biome, precipitation, and tropicality. Autotomy in limbless reptiles was affected by size-dependent factors that interplay with ontogeny and sexual dimorphism, although size-independent effects of life-stage and sex also shaped behavioural responses to predators. The increase in probability of tail loss with verticality and diurnality suggests a risk-balance mechanism between species habitat use and activity pattern. Although autotomy is more likely in warmer regions, it seems unrelated to seasonal differences in snakes and amphisbaenians activity. Our findings reveal several processes related to predator-prey interactions involving limbless reptiles, demonstrating the importance of scientific collections to unveil ecological mechanisms at different spatio-temporal scales.

Chance, luck and a fortunate finding: a new species of watersnake of the genus Helicops Wagler, 1828 (Serpentes: Xenodontinae), from the Brazilian Pantanal wetlands.

We describe a new watersnake of the genus Helicops based on a single specimen found in the northern limit of the Brazilian Pantanal. Immediately after collection, the unique features of color pattern and head proportions prevented us to attribute this specimen to any other congener. Further comparisons revealed that the combination of entire nasal scales, a distinctively acuminate snout, high dorsal and supralabial counts, as well as a dorsal pattern with chain-like spot rows and a venter with vivid and peculiar orange markings confirmed that the specimen represented a new species. Molecular data supported our morphological conclusion recovering the new species deeply nested within Helicops terminals, sister to a clade composed by H. carinicaudus and H. nentur. Our discovery represents a rare instance of a snake species restricted to the Brazilian Pantanal, but we refrain from considering it a Pantanal endemic until further records allow more considerations on distributional patterns.

The taxonomic status of the "forgotten" Bolivian snakes, Atractus balzani Boulenger 1898 and Atractus maculatus (sensu Boulenger 1896) (Serpentes: Dipsadidae).

The genus Atractus Wagler 1828 comprises almost 150 currently recognized species of cryptozoic snakes widespread in the Neotropics, occurring from Panama to northeastern Argentina (Passos et al. 2016a). Despite the publication of the descriptions of several new species within the last decade, the taxonomy of the genus is unclear in some instances. This is mainly due to the fact that a number of poorly delimited taxa still exist (Passos et al. 2018). The most frequent problem faced by taxonomist working with the genus Atractus is the lack of specimens available for several species, most of them only still being known from their types, a situation that considerably weakens the definition of species boundaries between closely related taxa (Passos et al. 2010a, 2013). More importantly, many of the previously recognized species may represent aberrant individuals with unusual or abnormal scale counts, anomalous azygous or fused cephalic plates, infrequent polychromatic patterns, or any combination of these states (see Passos et al. 2016b). In the course of a thorough taxonomic review of the genus (Passos 2008; Passos et al. 2018), an effort has been made to examine all of the available types (including those apparently lost or misplaced in collections) and material of historical importance that was previously referred to the genus in the literature, and these were then compared to newer samples collected more recently. During the examination of the collections of the Natural History Museum of London and the Museo Civico di Storia Naturale of Genova, we found important specimens of Atractus from Bolivia. However, in order to better understand all the problems related to these old and "forgotten" Bolivian snakes, we need to examine their history.