Alligators in the big city: spatial ecology of American alligators (Alligator mississippiensis) at multiple scales across an urban landscape

Abstract

Urbanization impacts wildlife, yet research has been limited to few taxa. American alligators (Alligatormississippiensis) are apex predators that have received minimal attention within urban areas. We investigated potential effects of urban land use on alligators through surveys of relative alligator abundance in nine tributaries of the lower St. Johns River within Jacksonville, FL. We then explored the potential effects of urban development on alligator spatial distribution and habitat selection at coarse and fine scales. At the coarse scale, we found no correlation between percent developed land and alligator abundance across tributaries; instead, salinity was the primary driver. However, at the fine scale alligators preferred habitats with more open water and vegetated shorelines and avoided anthropogenic structure. Surprisingly, only one of 93 sighted individuals was an adult. Hunting and nuisance alligator data suggests that adults are relatively rare in Jacksonville because they have been targeted for removal. Thus, smaller alligators still occupy urban habitats because they are not targeted and face no competition from adults. Increasing urbanization and human activity may further degrade alligator habitats and limit the distribution of breeding adults, potentially leading to local population declines.

Golf course living leads to a diet shift for American alligators

“…We divided BIC by TNW to generate an index of specialization that varied between 0 and 1, where 0 represents a population of pure generalists (individuals exactly overlap with population's resource use) and 1 represents a population of pure specialists (individuals do not overlap with other individuals in the population). Calculations of BIC/TNW are biased by individuals that only contain one prey group (Bolnick et al, 2002), so we excluded individuals who only contained one or two prey items within the same prey group and nothing else. Specialization metrics like BIC/TNW can be difficult to compare across populations if the numbers of available prey types across different habitats are not considered.…”

“…For example, resurgent Nile crocodile ( Crocodylus niloticus ) populations in Namibia have increasingly come into conflict with humans in areas now used for cattle ranching (Aust et al, 2009 ), and estuarine crocodiles ( Crocodylus porosus ) in Malaysian Borneo are becoming common residents of oil palm plantations (Evans et al, 2016 ). While there have been a few studies of crocodilian populations in human‐dominated areas, most have aimed only to investigate population distribution and habitat use (e.g., Beal & Rosenblatt, 2020 ; Eversole et al, 2018 ; Skupien & Andrews, 2017 ), rates of human–crocodile conflict (e.g., Garcıa‐Grajales & Buenrostro‐Silva, 2019 ; Uluwaduge et al, 2018 ; Wallace et al, 2011 ), or population management techniques (Kidd‐Weaver et al, 2022 ). As a result, it remains unclear how crocodilian ecology, and especially feeding patterns, might shift in areas that have undergone land use change.…”

Blood concentrations of per- and polyfluoroalkyl substances are associated with autoimmune-like effects in American alligators from Wilmington, North Carolina

“…Alligators living along the Cape Fear River are non-migratory apex predators with a life span exceeding 60 years that co-utilize human habitats contaminated with PFAS ( Elsey et al, 2019 ). The aim of this study was to evaluate exposures and impacts of long-duration PFAS exposure on biomarkers of immune health in American alligators ( Alligator mississippiensis), a top trophic carnivore at the human/wildlife interface of both rural and urban environments ( Beal and Rosenblatt, 2020 ; Somaweera et al, 2020 ). Because the innate immune system is conserved across taxa and it is generally robust and highly protective in alligators ( Merchant and Britton, 2006 ; Finger and Gogal, 2013 ), we predicted that alligators would serve as sensitive sentinels of cumulative adverse immune health resulting from PFAS exposures common to humans living in the Cape Fear River basin.…”

Blood Concentrations of Per- and Polyfluoroalkyl Substances are Associated with Autoimmunity-like Effects in the American Alligator

“…The aim of this study was to evaluate the impacts of long-duration PFAS exposure on American alligators ( Alligator mississippiensis ), a top trophic carnivore at the human/wildlife interface of both rural and urban environments (Beal and Rosenblatt 2020; Somaweera et al 2020). Alligators, renowned for their robust and highly protective immune systems, are an especially important aquatic biomonitoring and predictive sentinel species of adverse outcomes resulting from integrated effects of persistent toxic chemicals (Crain and Guillette 1998; Guillette et al 2000; Finger and Gogal 201; Pérez and Wise 2018).…”