Encroachment of humans into pristine habitats is a major threat to biodiversity. We found that some paleotropical bat species from disturbed forests suffered from chronic stress and an impaired immune system, suggesting that allostatic overload may play a pivotal role in the extinction of wildlife species.
Anthropogenic habitat disturbance is a major threat to biodiversity worldwide. Yet, before population declines are detectable,
individuals may suffer from chronic stress and impaired immunity in disturbed habitats, making them more susceptible to
pathogens and adverse weather conditions. Here, we tested in a paleotropical forest with ongoing logging and fragmentation,
whether habitat disturbance inﬂuences the body mass and immunity of bats. We measured and compared body mass, chronic
stress (indicated by neutrophil to lymphocyte ratios) and the number of circulating immune cells between several bat species
with different roost types living in recovering areas, actively logged forests, and fragmented forests in Sabah, Malaysia. In a
cave-roosting species, chronic stress levels were higher in individuals from fragmented habitats compared with conspeciﬁcs
from actively logged areas. Foliage-roosting species showed a reduced body mass and decrease in total white blood cell
counts in actively logged areas and fragmented forests compared with conspeci ﬁ cs living in recovering habitats. Our study
highlights that habitat disturbance may have species-speciﬁ effects on chronic stress and immunity in bats that are poten-
tially related to the roost type. We identiﬁed foliage-roosting species as particularly sensitive to forest habitat deterioration.
These species may face a heightened extinction risk in the near future if anthropogenic habitat alterations continue.