This blog post is provided by Mario Moura and Henrique Costa and tells the #StoryBehindthePaper for the paper “Unwrapping broken tails: biological and environmental correlates of predation pressure in limbless reptiles“, which was recently published in the Journal of Animal Ecology. In their study, they use natural history collections of snakes and limbless lizards from museums to explore where predation occurs. These animals can drop their tails as a response to a predator, giving them a chance to escape. Using specimens the authors explored when and where this happened and to which species and animals, exploring predation risk across the group.
This post is also available in Portuguese here.
What can a tail tell you? If we are talking about dogs and you are fluent in canine body language, it may say a lot. But what if we are discussing tails on snakes and worm-lizards? Before someone starts picturing a snake wagging its tail, let us bring a bit of morbidity here. Because some species interactions are quite difficult to observe in nature, scientists can rely on preserved specimens to reveal mysteries about animal behaviours. By examining more than eight thousand preserved specimens deposited across 61 scientific collections, a team of 34 scientists from South America, North America and Europe elucidated which factors influence tail loss in snakes and worm-lizards, a defensive behaviour also known as ‘caudal autotomy’ and often used to escape predation.
Many animal species, from crabs and octopuses to salamanders and lizards can lose a body appendage (a leg or a tail, for example) to escape predation. But some animals regenerate body parts, which can make it difficult to investigate the relationship between the occurrence of autotomy events and other biological and environmental factors. However, in contrast with “typical lizards” whose tail regenerates, snakes and worm-lizards (a group of underground limbless lizards named ‘amphisbaenians’) can lose their tail only once*. The uniqueness of this behaviour in these limbless reptiles makes them an ideal group to investigate drivers of predation pressure in nature.
For each preserved specimen, the team examined whether the tail was intact or broken and scarred, and gathered information on multiple factors including the species identity, size, sex, activity (diurnal or nocturnal), habitat use (fossorial, terrestrial, aquatic, arboreal), and environmental conditions (temperature, precipitation, biome, among others) from the location where the specimen was collected. The specimen database was used to assess which biological and environmental factors (if any) affect the probability of tail loss in limbless reptiles. The study just published in Journal of Animal Ecology is part of a Special Feature on Leveraging Natural History Collections to Understand the Impacts of Global Change, and illustrate the importance of scientific collections to improve our biodiversity knowledge.
In unwrapping novel information on the biology of 33 species of snakes and 11 species of worm-lizards, we show that larger and female specimens were more likely to show tail loss. Within the same species, larger specimens are usually older and had more opportunities of being face to face with a predator, escaping while leaving their tail behind. Our findings suggest that male specimens are less prone to losing their tail, probably because the tail also holds the copulatory organs (hemipenes) hidden in its base. Therefore, if a predator bites an extra bit of tail, male snakes and worm-lizards may face some issues when mating.
The study revealed that limbless reptiles from warmer regions, living on trees and with diurnal habits rely most on caudal autotomy. For instance, the tail loss record holder was the Gouvea’s Sipo snake (Chironius gouveai), a diurnal and arboreal species from southern Brazil in which 75% of preserved specimens show lost tails. The accumulated evidence suggests that arboreal snakes have fewer places to hide relative to ground dwelling and aquatic snakes, or the worm-lizards with their underground lifestyle. The fact that most reptile predators (most birds and reptiles) enjoy hunting during daylight, means that tree climbing has become a dangerous tour whose ticket might be one snake’s tail.
The Gouvea’s Sipo snake (Chironius gouveai) from southern Brazil was the species with highest number of specimens with lost tails. (Photo: Daniel Loebmann)
How can this tale of lost tails be tied up with global change? Well, our study also showed that snakes and worm-lizards from warmer regions have more chance of losing their tails. Reptiles are ectothermic, which means they depend on environmental temperature to heat their bodies. So, specimens experiencing warmer temperatures may be more active and experience a higher chance of encountering a predator asking for a ‘tail tip’. Alternatively, warmer regions may have higher predation pressure, as already demonstrated for lower latitudes and elevations.
Natural history museums and collections are true biodiversity libraries, and the specimens they house can tell us many things about the past, present, and even the future of our planetary life. Preserved specimens have been serving in studies for centuries, from the science of taxonomy (the “cataloguing and classification of life”) to multiple aspects of species biology, such as diet, reproduction, malformations, parasites, defensive behaviours like tail autotomy, and much more. We hope our study helps demonstrate how scientific collections are a priceless source for research on the endless secrets of life on Earth.
Read the paper
Read the full paper here: Moura, M. R., Costa, H. C., Abegg, A. D., Alaminos, E., Angarita-Sierra, T., Azevedo, W. S., Cabral, H., Carvalho, P., Cechin, S., Citeli, N., Dourado, Â. C. M., Duarte, A. F. V., França, F. G. R., Freire, E. M. X., Garcia, P. C. A., Mol, R., Montero, R., Moraes-da-Silva, A., Passos, D. C. … Guedes, J. J. M. (2022). Unwrapping broken tails: Biological and environmental correlates of predation pressure in limbless reptiles. Journal of Animal Ecology, 00, 1– 14. https://doi.org/10.1111/1365-2656.13793
* In some snakes, the tail can break in different points and although the tail does not regenerate, the snake might lose small parts of the tail at different moments.