Movement patterns of Nilgai antelope (Boselaphus tragocamelus) in South Texas: implications for cattle fever tick management

Authors: FOLEY, AARON - Texas A&M University; Goolsby, John; ORTEGA JR, ALFONSO - Non ARS Employee; ORTEGA SR, ALFONSO - Texas A&M University; Perez De Leon, Adalberto - Beto; HEWITT, DAVID - Texas A&M University; CAMPBELL, TYLER - East Foundation; SINGH, NIRBHAY - University Of Montpellier

Submitted to: Journal of Wildlife Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2017
Publication Date: 10/1/2017
Citation: Foley, A.M., Goolsby, J., Ortega Jr, A., Ortega Sr, A., Perez De Leon, A.A., Hewitt, D.G., Campbell, T., Singh, N.K. 2017. Movement patterns of Nilgai antelope (Boselaphus tragocamelus) in South Texas: implications for cattle fever tick management. Journal of Wildlife Management. 146:166-172.

Interpretive Summary: Cattle fever ticks (CFT) Rhipicephalus (=Boophilus) microplus and Rhipicephalus annulatus are invasive livestock pests that are endemic to Mexico and invasive along the Texas – Mexico border. Acaricide resistance, alternate wildlife hosts, and pathogenic landscape forming weeds present challenges for sustainable eradication of this pest in the U.S. CFT are the vector for bovine babesiosis, a lethal disease causing high mortality particularly in susceptible European breeds of cattle and severely affecting the beef cattle industry. Efforts to eradicate CFT from the United States have been successful; however, a quarantine area is maintained between Texas and Mexico to check its entry from the infected areas of neighboring Mexico states as wildlife and stray cattle that carry CFT can freely cross the border. In recent years, there has been an increase in CFT infestations outside of the quarantine area in Texas. Nilgai (Boselaphus tragocamelus), an exotic Asian antelope widely distributed in southeastern Texas, carry CFT and are therefore of interest in terms of understanding how CFT may be spread through the landscape. Thirty nilgai of both sexes and different age classes were captured and fitted with satellite radio collars in South Texas to gain information about movement patterns, response to disturbances, and movement barriers. The year-round home range sizes were similar but highly variable between females (16,000 acres, range =1200-40,000) and males (12,000 acres, range = 1600-60,000). There appeared to be seasonality in female movement patterns with peaks occurring during June-August, most of which were attributed to young females. These peaks appeared to be a function of break-ups in social groups rather than environmental conditions. Nilgai, which reportedly are sensitive to disturbance, were more likely to relocate into new areas immediately after being captured versus 4 other types of helicopter activities. Nilgai apparently did not cross the 4 foot high cattle fences parallel to paved highways. Results indicate that females, particularly the young ones, have a higher chance of spreading CFT though the landscape than males but spread of CFT may be mitigated via maintenance of fences running parallel with paved highways. However, more information on basic ecology and biology of nilgai is needed to better interpret movement patterns to formulate and implement effective CFT management strategies.

Technical Abstract: Cattle fever ticks (CFT) are the vector for the etiological agent of bovine babesiosis, a lethal disease causing high mortality particularly in susceptible Bos taurus populations and severely affecting the beef cattle industry. Efforts to eradicate CFT from the United States have been successful; however, a quarantine area is maintained between Texas and Mexico to check its entry from the infested areas of neighboring Mexico states as wildlife and stray cattle that carry CFT can freely cross the border. In recent years, there has been an increase in CFT infestations outside of the quarantine area in Texas. Nilgai (Boselaphus tragocamelus), an exotic Asian antelope widely distributed in southeastern Texas, carry CFT and are, therefore, of interest in terms of understanding how CFT may be spread through the landscape. Thirty nilgai of both sexes and different age classes were captured and fitted with satellite radio collars in South Texas to gain information about movement patterns, response to disturbances, and movement barriers. Mean year-round home range sizes were similar but highly variable between females (8,234 ha, range = 733-20,864) and males (6,626 ha, range = 851-31,533). There appeared to be seasonality in female movement patterns with peaks occurring during June-August, most of which were attributed to young females. These peaks appeared to be a function of break-ups in social groups rather than environmental conditions. Nilgai, which reportedly are sensitive to disturbance, were more likely to relocate into new areas immediately after being captured versus 4 other types of helicopter activities. Nilgai apparently did not cross the 1.25 m high cattle fences parallel to paved highways. Results indicate that females, particularly the young ones, have a higher chance of spreading CFT though the landscape than males but spread of CFT may be mitigated via maintenance of fences running parallel with paved highways. However, more information on basic ecology and biology of nilgai is needed to better interpret movement patterns to formulate and implement effective CFT management strategies.