A new study by a team of international scientists led by Professor Liliana M. Dávalos of Stony Brook University and Professor Samuel Turvey of the Zoological Society of London shows that the largest and smallest mammals in the Caribbean were the most vulnerable to extinction. The results, published in the Proceedings of the Royal Society B, help predict future risk of extinction and provide information on the conservation strategies needed to prevent future loss of biodiversity.
Sloths, rodents, and primates – some of the largest and smallest mammals on Caribbean islands – are among the most critically endangered. Photo credit: David Rini, Johns Hopkins University
Most previous studies have found that larger mammals are more likely to become extinct, so the results of this study are unusual. The paper, titled “Where the Wild Things Were,” examined past extinction patterns in Caribbean mammalian fauna to help scientists understand the factors that predispose species to extinction. When the mammals became extinct, they found that size actually matters in life.
The islands of the Caribbean have long been a source of fascination for scientists and conservationists. They were once home to a wide variety of land mammals, including sloths, primates, unusual insectivores, and giant rodents, but the arrival of various waves of human colonists from around 6,000 years ago sparked the largest series of human-made mammalian deaths since the end of the last Ice Age.
Only 11 native Caribbean rodents and two insectivores survive today – including the two solenodons, large shrew-like mammals that have the unique ability to inject venom into their prey using modified grooved teeth. Both Solenodon species are the only representatives of an ancient line of mammals that differed from the ancestors of all other living mammals during the time of the dinosaurs, about 76 million years ago.
Dávalos, professor at the Institute of Ecology and Evolution at the College of Arts and Sciences, designed and completed the statistical analyzes that led to the results. By conducting the study at the mammalian population rather than species level, the team’s methods were able to take into account the effects of different environmental conditions on different islands on species’ chances of survival.
The study conducted a comprehensive analysis that included records of extinction patterns from 219 terrestrial mammal populations on 118 Caribbean islands. It went beyond previous research on the extinction of Caribbean mammals, which mainly focused on reconstructing the dates of the last appearance of extinct species and assigning them to specific historical events. Instead, this study sought to identify broader ecological patterns – such as the relationship between body mass and risk of extinction – that affect a mammal’s chances of survival in response to human activity.
They found that medium-sized Caribbean mammals – like the Solenodons – were less sensitive to extinction when compared to their smaller and larger counterparts.
According to Dávalos and co-authors, this general discovery likely reflects the fact that larger species were more susceptible to previous human hunting, while smaller species were more susceptible to predation or competition from introduced species such as mongooses and rats.
“To answer questions like ‘What traits predispose species to survival?’ Or “Which island features are associated with extinction?” We examined every population on an island as a natural experiment, “says Dávalos.” With enough of them, patterns emerge that have often been discussed but could not be quantified, without the large ones Database of many natural experiments in the Caribbean and powerful computational approaches there is no way to answer these questions.
The analyzes also showed that Caribbean mammals of all sizes were less likely to survive on the earliest colonized islands than on tiny, low-lying offshore islands, meaning their future survival could be threatened by climate change and rising sea levels, if so no measures are taken to protect these vital natural refuges. “
“To prevent the extinction of critically endangered species, one must not only consider the immediate risks to their survival, but also the history of man-made biodiversity loss and the unique knowledge that the past has about the vulnerability or resilience of species under different conditions can deliver, ”adds Professor Turvey.
“The Caribbean islands are home to a unique diversity of mammals that has tragically been almost completely wiped out by previous human activity. Our study clearly shows the importance of learning from the past in order to make the future better. We must use information from the historical, archaeological, and recent fossil record to educate about conservation today, or we risk losing these remarkable species forever. “
The research for this study was supported in part by the National Science Foundation (NSF). Additional NSF funding enabled analysis of the SeaWulf computer system at the Institute for Advanced Computational Science at Stony Brook University.