Post-Release Ecology of Rehabilitated Hoffmanns' Two-toed Sloths in Panamá

Author

Chelsea Nicole Morton, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2021

Degree Name

Master of Science

Department

Forestry

First Advisor

Nielsen, Clayton

Abstract

The field of wildlife rescue and rehabilitation continues to grow as human expansion increases the rate of deforestation in Latin America. Wild animals that are often rescued from becoming orphaned or injured are rehabilitated in captivity until considered suitable for release back into the wild. Sloths (Bradypus spp. and Choloepus spp.) are a common species admitted to rescue centers throughout Latin America due to their poor dispersal abilities and vulnerability to anthropogenic impacts. Post-release monitoring is fundamental in measuring the success of wildlife rescue programs, however, few studies have assessed the outcomes of releasing hand-reared sloths back into the wild. I studied the ecology of rehabilitated and relocated Hoffmann’s two-toed sloths (C. hoffmanni) in central Panamá. My objectives were to: (1) use a soft-release technique to quantify activity budgets of individuals prior to release in the wild, (2) analyze movement trajectories and estimate home range sizes, (3) assess habitat selection, and (4) determine survival rates and causes of mortality for rehabilitated and released two-toed sloths. Eleven two-toed sloths rescued from the wild were hand-reared in captivity for a mean total of 727  193 days (mean  SE value across all sloths) at the Pan-American Conservation Association facilities in Colón Province, Panamá. During 2019-2020, sloths were processed into 2 groups, radiomarked, placed in an outdoor 500 m2 soft-release enclosure for 3 months, and released in nearby Soberanía National Park. I conducted 580 hr of behavioral observations during soft-release to quantify activity budgets for 5 main activity states. A linear mixed model was used to compare two-toed sloth activity budgets in response to sex, age, season (i.e., dry vs. wet), session time (i.e., morning vs. evening) and month. Rehabilitated two-toed sloths spent 80.0% of their time resting, becoming active and more alert in the evening, exhibiting behavioral patterns similar to wild two-toed sloths (as ascertained from existing literature). I used homing to radiotrack two-toed sloths for 210 radio-days during which I used a paired analysis approach to measure tree height, crown height, height to crown base, diameter at breast height, abundance of lianas, canopy depth, and canopy closure at 118 used and random locations. Habitat selection was modeled using conditional logistic regression and movement trajectories were analyzed using ArcGIS. Rehabilitated two-toed sloths traveled shorter distances than wild two-toed sloths, traveling a mean linear distance of 82.3  21.6 m and a mean distance of 25.6  9.5 m between successive locations. Mean home range size for released two-toed sloths was 2.92  1.19 ha with females occupying larger areas than males. I did not find strong evidence of habitat selection; however, rehabilitated two-toed sloths chose trees with a smaller dbh than available. Habitats used by rehabilitated two-toed sloths closely resembled those used by wild two-toed sloths, selecting trees with dense crowns and 50% lianas. Monthly survival for rehabilitated two-toed sloths (0.72  0.14) was low relative to wild sloths, and monthly estimates for males (1.00  0.00) and females (0.44  0.22) did not differ (P  0.30). Eight mortalities were recorded with predation and natural causes being the main causes of mortality. My study provides information that can be useful in evaluating the costs and benefits of sloth rescue and rehabilitation programs throughout Latin America.