Bat communities and activity along a coastal zone in Puerto Rico: Risk from climate change
Bats provide critical ecosystem services and are the most abundant mammals in many habitats, particularly in tropical regions. Tropical islands, on the other hand, are depauparate compared to mainlands. Their coastlines are being rapidly developed and are additionally at risk from sea-level rise that may stem from climate change. It is known that bats use mainland coastlines during migration. On islands, these transition zones are highly productive and may offer good foraging habitat, but little is known about bats’ coastal zone use. Our project explored bat activity in different habitats and in proximity to the ocean around Cabo Rojo on the Southwestern corner of Puerto Rico.
To determine what effect habitat changes may have on bat communities, we examined bats’ current use of different habitats. We asked: Does habitat and proximity to the ocean change bat species composition and level of activity? We used ultrasonic acoustic recordings to determine bat community composition and activity in different habitats, including small islands off the coast, coastal habitats, suburban yards, wildlife reserves, and inland mountains.
In Cabo Rojo and environs, we recorded for 66 unit-days and collected over 9000 bat calls. Through analysis of these recordings and mistnetting, we found five species (of the 13 found on Puerto Rico): Noctilio leporinus (Fishing Bat), Pternotus parnellii (Parnell’s Mustached Bat), Pternotus quadridens (Sooty Mustached Bat), Lasiurus borealis (Eastern Red Bat), and Molossus molossus (Velvety Free-tailed Bat). While inland areas with buildings had the most bat activity, species richness was greater in inland habitats with natural vegetation; and bat commuting and foraging near and on offshore islands were not trivial, especially for certain species. For example, we recorded L. borealis primarily around mangroves, and recorded bats on mangrove islands (up to 1.6 km) off the mainland.
Sea level rise could impact almost all coastal areas in Puerto Rico, but especially low-lying mangroves in front of steeper terrain. The implications for all species through loss of land area will be intense; while none of the bats we found are listed as endangered, habitat change (e.g. loss of mangrove habitat) may directly impact bat populations. This loss may then cascade to other species associated with bats (the Puerto Rican boa, avian predators, trees and plants such as Stahlia monosperma). Potentially, the greatest impact may be an increase of pest insects if bats decline extensively.