Effects of roost specialization on extinction risk in bats

Abstract

Understanding causes and consequences of ecological specialization is of major concern in conservation. Specialist species are particularly vulnerable to human activities. If their food or habitats are depleted or lost, they may not be able to exploit alternative resources, and population losses may result. We examined International Union for Conservation of Nature (IUCN) Red List bat data and the number of roosts used per species (accounting for phylogenetic independence) to determine whether roost specialization is correlated with extinction risk. We found a significant correlation between the IUCN Red List category and the number of roost types used. Species that use fewer roost types had a higher risk of extinction. We found that caves and similar structures were the most widely used roost types, particularly by species under some level of risk of extinction. Many critically endangered, endangered, or vulnerable species used natural roosts exclusively, whereas less threatened species used natural and human-made roosts. Our results suggest that roost loss, particularly in species that rely on a single roost type, may be linked to extinction risk. Our focus on a single life history trait prevented us from determining how important this variable is for extinction risk relative to other variables, but we have taken a first step toward prioritizing conservation actions. Our results also suggest that roost specialization may exacerbate population declines due to other risk factors, such as hunting pressure or habitat loss, and thus that management actions to preserve species under risk of extinction should prioritize protection of roosting sites.

Understory bat roosts, availability and occupation patterns in a Neotropical rainforest of Costa Rica

“…Roosts are a fundamental part of the life history of bats (Kunz, 1982), so the presence of this resource is essential to reproduction and survival of populations (Kunz, 1982;Kerth, 2008;Sagot & Chaverri, 2015). Conservation efforts for bats must include protection of roost resources (Kunz & Lumsden, 2003), especially if we take into account that human activities are increasingly turning large forested areas into mixed landscapes, fragmented areas and manmade structures (Daily, Ceballos, Pacheco, Suzán, & Sánchez-Azofeifa, 2003;Laurance, 2004;Tabarelli, Pinto, Silva, Hirota, & Bede, 2005) that reduce and change the availability of important roost resources (Kunz & Lumsden, 2003).…”

“…Conservation efforts for bats must include protection of roost resources (Kunz & Lumsden, 2003), especially if we take into account that human activities are increasingly turning large forested areas into mixed landscapes, fragmented areas and manmade structures (Daily, Ceballos, Pacheco, Suzán, & Sánchez-Azofeifa, 2003;Laurance, 2004;Tabarelli, Pinto, Silva, Hirota, & Bede, 2005) that reduce and change the availability of important roost resources (Kunz & Lumsden, 2003). Additionally, more specialized species are restricted to the use of a narrow set of available roosting resources, which may increase their risk of extinction (Sagot & Chaverri, 2015). For example, considering the specialized roosting requirements of some bat species recorded in the area (Timm & Mortiner, 1976;Kalko et al, 2006;Rodríguez-Herrera et al, 2008;Solano-Quesada & Sandoval, 2010), the low roost density of species like Ectophylla alba and Lophostoma brasiliense, in addition to the rarity of species like Thyroptera tricolor, T. discifera, Vampyriscus nymphaea and Lophostoma silvicolum, these species could be considered as highly vulnerable to a decrease in available roosting resources in our study area.…”

“…Finally, even in small forest fragments such as TBR, preserving natural shelters like fallen and hollow tree trunks, termite nests, tents and caves is a forward step to conservation of bat populations and the ecological services they provide (Sagot & Chaverri, 2015).…”

Trait-dependent tolerance of bats to urbanization: a global meta-analysis

“…We further classified species into roosting generalists or specialists. Hereby, we only considered natural roosts (caves, rocks and crevices, tree hollows, bark and trunk, foliage and plant structures) based on the most common term in the literature (following [24]) and excluded reports from artificial roosts such as bat boxes or roosts in buildings as these represent human influence, which is always greater in urban compared with non-urban areas. If a species was only reported roosting in one of such categories listed above, we considered it as a roosting specialist; if it was reported to use various types of roosts, we classified it as a roosting generalist.…”

Social communication in bats

“…Many types of structures are used as roosting sites by bats. Caves, for example, are used by a large proportion of bat species worldwide (Sagot & Chaverri, 2015), and are the most permanent roosting structure known (Lewis, 1995;Altringham, 2011), often used by bat colonies for many years. Roosting structures also include buildings, hollow trees or tree cavities, termite nests, the flowers of carnivorous pitcher plants, and modified leaves, among many others (Kalko, Ueberschaer & Dechmann, 2006;Altringham, 2011;Grafe et al, 2011).…”