Cost, effort and outcome of mammal rediscovery: Neglect of small species

There is often intense public interest in the process of rediscovery of species that were presumed extinct, although rediscovered mammals are typically small, inconspicuous inhabitants of tropical forests. Conservation actions for small species are relatively inexpensive compared to the interventions required to protect charismatic, large mammals. However, threatened small mammals such as rodents, bats, shrews and small marsupials attract less research attention, conservation actions, space in zoos, and funding than larger species, and most threatened small mammals receive no attention, particularly those in tropical forest habitats. I investigated how the body size of rediscovered mammals has changed during the last century, how body size is associated with search and conservation effort and subsequent recovery, and the success of recovery actions for rediscovered mammals. There has been a strong decline in the mean body size of rediscovered mammals since the 19th century. Smaller species were missing for longer before rediscovery, and attracted less search effort. Cost estimates were lower in recovery plans for smaller rediscovered mammals. Despite this, increasing population trend after rediscovery was associated with larger body size, and larger species recovered better with conservation effort, although small species declined despite conservation effort. All species with no conservation actions (the majority of small species) were declining. Sixty percent of rediscovered mammals remain critically endangered or endangered, and 8% (6 species) are likely to be extinct. I argue that conservation outcomes for rediscovered mammals could be greatly improved by a modest increase in attention to small-bodied species.