Bat cellular immunity varies by year and dietary habit in an increasingly fragmented landscape

Monitoring the health of wildlife populations is essential in the face of increased agricultural expansion and forest fragmentation. Loss of habitat and habitat degradation can negatively affect an animals physiological state, possibly resulting in immunosuppression and increased morbidity or mortality. We sought to determine how fragmentation may differentially impact cellular immunity and infection risk in Neotropical bats species regularly infected with bloodborne pathogens, and to evaluate how effects may vary over time and by dietary habit. We studied common vampire bats (Desmodus rotundus), northern yellow-shouldered bats (Sturnira parvidens), and Mesoamerican mustached bats (Pteronotus mesoamericanus), representing the dietary habits of sanguinivory, frugivory, and insectivory respectively, in northern Belize. We compared estimated total white blood cell counts, leukocyte differentials, and infection status with two blood-borne bacterial pathogens (Bartonella spp. and hemoplasmas) of 118 bats captured in a broadleaf, secondary forest over a three-year period (2017-2019) of increasing habitat fragmentation. We found evidence for bat species-specific responses of cellular immunity between years, with neutrophil counts increasing in D. rotundus, but decreasing in S. parvidens and P. mesoamericanus from 2018 to 2019. However, the odds of infection with Bartonella spp. and hemoplasma spp. between 2017 and 2019 did not differ between bat species, contrary to our prediction that pathogen prevalence may increase with increased fragmentation. We conclude that each bat species invested differently in cellular immunity in ways that changed over years of increasing fragmentation. We recommend further research on the interactions between habitat fragmentation, cellular immunity, and infection across dietary habits of Neotropical bats for informed management and conservation.