In the last issue of Conservation Biology M. Sagot and G. Chaverri present a new paper called “Effect of roost specialization on extinction risk in bats”. Link to the article.

The study of bats’ roosts is very important for different reasons. First, bats spend at least half of their life in the roost. They are also protected from predators and inclement weather. Finally, it is well known that roosts are used for rearing young. All these factors make roosts vital for the survival and reproduction of bat species. Roosts also provide, a very important location for social interactions, like copulation, grooming and feeding. 

Pygmy round-eared bat (Lophostoma brasiliense), roost in termite nests

Pygmy round-eared bat (Lophostoma brasiliense), roost in termite nests

Shaggy bat (Centronycteris maximiliani), roost in foliage

Shaggy bat (Centronycteris maximiliani), roost in foliage

Bats use a variety of roosts like caves, cliffs, tree cavities, banks and ledges, tree bark, human-made buildings and structures, leaf litter, tree boles, bamboo culm, modified leafs as tents, stems, foliage, termite nests, bird nests and furled leaves. Some species use several roost types and others use only one kind of structure and are roost specialists. 

The article by Sagot and Chaverri tested the hypothesis that “species that use fewer roost types are at greater risk extinction, as defined by the International Union for Conservation of Nature (IUCN) Red List of Threatened Species”. IUCN uses different categories for its list: CR, critically endangered; EN, endangered; VU, vulnerable; NT, near threatened; and LC, least concern. 

round ~24% of all bat species are under some kind of threat as a result of anthropogenic activities. The article focuses on 385 bat species (18 families and 128 genera) distributed worldwide. The species displayed a diverse range of diets (carnivorous, piscivorous, sanguinivorous, nectarivorous, insectivorous and frugivorous).

Spix's disk-winged bat (Thyroptera tricolor), roost in furled leaves.

Spix's disk-winged bat (Thyroptera tricolor), roost in furled leaves.

Spix's disk-winged bat (Thyroptera tricolor) leaving the roost.

Spix's disk-winged bat (Thyroptera tricolor) leaving the roost.

From the 178 species in the study that used natural roost exclusively, 20% were critically endangered, endangered, or vulnerable. While, the 2 species of the study that used human-made roost exclusively were least concern.

They found that all critically endangered bat species lived on islands with a very small range size. Around 60% of species considered endangered and 50% of vulnerable species occurred only on islands. 

 

Chestnut sac-winged bat (Cormura brevirostris), roost under fallen trees.

Chestnut sac-winged bat (Cormura brevirostris), roost under fallen trees.

Chestnut sac-winged bat (Cormura brevirostris)

Chestnut sac-winged bat (Cormura brevirostris)

Their analysis found that species that used fewer roost types had a higher risk of extinction. The major threats for the species with highest extinction risk were mainly habitat degradation and roost loss. Additionally, roost loss and disturbance of animals at roost sites are considered the most recurrent causes of population decline in most threatened bat species. 

Honduran white bat (Ectophylla alba), roost under modified leafs (tents)

Honduran white bat (Ectophylla alba), roost under modified leafs (tents)

Honduran white bat (Ectophylla alba)

Honduran white bat (Ectophylla alba)

This article increases the importance of roosts in bat conservation, and the results of this study to project could help guide conservation priorities based on roost specialization. For example the Caribbean Islands have ~57 species of which ~28 are endemic; most of these species have a small range size and the use of different criteria including roost specialization could provide a stronger tool to establish conservation priorities for this region. 

Greater dog-like bat (Peropteryx kappleri), roost in caves and boulder crevices

Greater dog-like bat (Peropteryx kappleri), roost in caves and boulder crevices


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