Latrine ecology of nilgai antelope

Authors: ZOROMSKI, LISA - TEXAS A&M UNIVERSITY; DEYOUNG, RANDY - TEXAS A&M UNIVERSITY; Goolsby, John; FOLEY, AARON - TEXAS A&M UNIVERSITY; ORTEGA-S, J - TEXAS A&M UNIVERSITY; HEWITT, DAVID - TEXAS A&M UNIVERSITY; CAMPBELL, TYLER - EAST FOUNDATION

Submitted to: Journal of Mammalogy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2022
Publication Date: 6/17/2022
Citation: Zoromski, L.D., Deyoung, R.W., Goolsby, J., Foley, A., Ortega-S, J.A., Hewitt, D., Campbell, T. 2022. Latrine ecology of nilgai antelope. Journal of Mammalogy. https://doi.org/10.1093/jmammal/gyac056.
DOI: https://doi.org/10.1093/jmammal/gyac056

Interpretive Summary: Nilgai antelope are implicated in the long-range movement of southern cattle fever ticks, Rhipicephalus microplus, in the environment, especially in Cameron and Willacy Counties in South Texas. Treatment methods for nilgai are needed to support the Cattle Fever Tick Eradication Program. Remotely activated sprayers were developed for application of entomopathogenic nematodes at locations where nilgai congregate. Nilgai defecate repeatedly in single locations called latrines. Nilgai latrines were considered as possible treatment locations, but this research determined that they were mainly used by single nilgai bulls to mark territories. Therefore, treatment of nilgai at latrines with the remotely operated sprayer was not considered practical.

Technical Abstract: Nilgai antelope (Boselaphus tragocamelus) are native to India, Nepal, and Pakistan. Nilgai were introduced to Texas rangelands during the 1920s -1940s, and have since expanded into much of coastal South Texas and northern Mexico. Little is known about nilgai ecology in either their native or introduced ranges. One poorly understood aspect of nilgai ecology is their social system, which includes the use of latrines, or repeated defecation at a localized site. Latrines are common and highly visible, yet there has never been a formal study on nilgai latrine use. From April 2018–March 2019, nilgai latrines were studied at 3 sites in South Texas. Latrines were found to be abundant, with no evidence for selection based on vegetation communities, and were dynamic in persistence and visitation rates. Nilgai latrine densities were 3-10 times greater than population densities, indicating that individual nilgai must use multiple latrines. Camera traps and fecal DNA analysis revealed: latrine visits were mainly (70%) by nilgai bulls; latrines were mainly defecated on by nilgai bulls (89% for DNA samples, 92% in photos); visitations often (75%) occurred during the evening and night (1700–0459 hr); and the greatest frequency of visits (every 2-3 days on average) and number of latrines visited occurred during the peak of nilgai breeding season, was from December–February. Photographs and genetic analysis of feces indicated repeated visits from the same individuals. Nilgai cows occasionally used latrines and their use was sometimes followed by bulls showing flehmen responses (to bare upper teeth) after a nilgai cow defecated or urinated on the latrine. Photographic documentation of flehmen responses, mating, and fighting among bulls,also indicated that latrines were used by dominant bulls for territory demarcation and display of social dominance to both cows in estrus and subordinate bulls. Cows likely use latrines to communicate reproductive status. This study is the first assessment of the importance of latrines for nilgai social communication. Results provide basic ecological information on nilgai movements and behaviors, which will help managers better create management plans for this species in their introduced and native ranges.