Vasectomies of male African elephants as a population management tool: A case study

Abstract

Elephant populations in South Africa are largely confined to fenced reserves and therefore require continued management to prevent high elephant densities that may cause habitat degradation. Growing human populations surrounding these reserves limit the possibility for wildlife range expansion, adding socio-economic considerations to the growing list of challenges reserve managers must contend with. Often, reserves have therefore opted to manage elephant population growth using various contraceptive methods to reduce birth rates, with lethal control acting as a last resort.Reserve owners at the Pongola Game Reserve South in northern KwaZulu-Natal opted to vasectomise the oldest male elephants to limit elephant population growth. Besides the reduction in birth rates, vasectomies were anticipated to have minimal impacts on behaviour. This study aimed to examine behavioural implications of treatment by monitoring musth, dominance and social behaviours of vasectomised males.Physical and behavioural observations of vasectomised males were recorded using instantaneous scan sampling and continuous focal samples of study individuals between 2011 and 2016. These data were also collected for non-treated adolescent males, with which to substantiate potential impacts of vasectomies.This case study has revealed that the behaviour of the vasectomised males was not influenced by vasectomies: musth was displayed as anticipated in the oldest males; a linear dominance hierarchy was maintained, headed by the oldest individual, and association patterns with female groups remained intact. Further, the younger non-treated males fell in line with the overall dominance hierarchy.This unique post-treatment study supports the use of vasectomies as a relatively cost-effective (one-off treatment), low-risk and successful tool for the management of elephant population growth, and an option which is preferable to both lethal control and hormonal contraceptives. Further research to establish the impacts of vasectomies on female behaviour and population dynamics is recommended.

Woody vegetation damage by the African elephant during severe drought at Pongola Game Reserve, South Africa

“…Total annual rainfall (mm, 2003–2015), mean (red line) = 552 mm (±( SD ) 167), Zitzer & Boult, 2018[Colour figure can be viewed at wileyonlinelibrary.com]…”

“…In 2012, there were a total of 77 (0.71 km −2 ) elephant individuals in the reserve (eight bulls, and 69 cows & juveniles), and in 2015, there were 83 (0.76 km −2 , 13 bulls and 70 females and juveniles). The population has only experienced an 8% growth rate over the four‐year study period despite vasectomies and the birth control hormone, GnRH, being used in an attempt to limit population growth (Doughty, Slater, Zitzer, Avent, & Thompson, 2014; Zitzer & Boult, 2018). Although density is lower than Kruger National Park (0.85 km −2 , Ferreira, Greaver, & Simms, 2017), concern among managers regarding elephant‐mediated change in vegetation remains high (Knights, 2012).…”

“…The climate is hot and arid, with a dry season (mean temperature 20.7°C, April-September) and wet season (mean temperature, 23°C, October-March). Rainfall varies annually with an average of 543 mm ± (SD) 167 (2003-2015,Figure 2,[Zitzer & Boult, 2018]). There was below average rainfall in 2014-2015 (total of 349.5 mm and 312 mm, respectively) caused by the changing El Nino weather cycles(Blamey, Kolusu, Mahlalela, Todd, & Reason, 2018;Bond & Midgley, 2019;Figure 2).…”

“…There was below average rainfall in 2014-2015 (total of 349.5 mm and 312 mm, respectively) caused by the changing El Nino weather cycles(Blamey, Kolusu, Mahlalela, Todd, & Reason, 2018;Bond & Midgley, 2019;Figure 2). Therefore, we used 'nondrought' to denote normal meteorological conditions in 2012-2013, and 'drought years' to denote below average annual rainfall during our data collection in 2014-2015.F I G U R E 2Total annual rainfall(mm, 2003-2015), mean (red line) = 552 mm (±(SD) 167),Zitzer & Boult, 2018 [Colour figure can be viewed at wileyonlinelibrary.com]…”

The African Elephant (<i>Loxodonta africana</i>): Mini-Review of an Endangered Species

“…Other examples of tactics used include: the presence of drones that disturb the elephants, forcing them to move away from human settlements [23]; the substitution of attractive crops as corn by alternatives crops, such as ginger and lemon grass, may represent an aid to agriculture because elephants consume less of these crops [24]; reproductive control of elephants to avoid overpopulation, male aggression and Human-Elephant Conflict (HEC), as it is referred in the review Somgird and collaborators (2017) [25], such as GnRH vaccination (non-invasive contraceptive method) [26] and vasectomy [27], and lethal control, which is not a viable solution, since in addition to represent a threat to the conservation of the species, the invasion of crops may not always be done by the same elephant [12].…”