Resolving a conservation dilemma: Vulnerable lions eating endangered zebras

PLoS One. 2018 Aug 29;13(8):e0201983. doi: 10.1371/journal.pone.0201983. eCollection 2018.

Abstract

When predators are removed or suppressed for generations, prey populations tend to increase and when predators are re-introduced, prey densities should fall back to pre-control levels. In cases of apparent competition where there are alternate abundant and rare prey species, rare species may decline further than expected or disappear altogether. Recently, concern about the impact of recovering predator populations on wildlife in Laikipia County, Kenya, has led to questions of whether lions (Panthera leo, IUCN Red List Vulnerable) exert top-down pressure on Grevy's zebra (Equus grevyi, IUCN Red List Endangered). We examined effects of lion predation on Plain's zebra (E. quagga, IUCN Red List Near Threatened) and Grevy's zebra populations in a 2,105 km2 area defined by lion movements. We used line transect surveys to estimate density of Grevy's (0.71/km2) and Plain's (15.9/km2) zebras, and satellite telemetry to measure movements for lions and both zebras. We tracked lions to potential feeding sites to estimate predation rates on zebras. We compared field-based estimates of predation rates on both zebras to random gas models of encounters that result in predation to ask if lions prey preferentially on Grevy's zebra at a sufficient rate to drive population declines. Lions preyed on Grevy's zebra significantly less than expected in 15 of 16 (94%) scenarios considered and lions preyed on Plain's zebras as expected or significantly less than expected in 15 of 16 scenarios. Population trend of Grevy's zebra indicates that the Kenya population may be stabilizing. Recruitment rate to the population has tripled since 2004, making it unlikely that lions are having an impact on Grevy's zebras. In Laikipia County, competitive displacement by livestock (Livestock: Grevy's zebra ratio = 864:1) and interference competition for grass with Plain's zebra (Plain's zebra:Grevy's zebra ratio = 22:1) are most likely the predominant threats to Grevy's Zebra recovery.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Biomass
  • Endangered Species*
  • Equidae / physiology*
  • Food Chain*
  • Lions / physiology*
  • Predatory Behavior

Grants and funding

Funding was provided by: NSF grants DBI:0963022, DBI:1255913, IOB:9874523, IIS:0705822 and IBN:030923, Chester Zoo, Cleveland Metroparks Zoo, Disney Foundation, San Francisco Zoo, Meeker Family Fund, Banovich Wildscapes Foundation, Zeitz Foundation, Donald and Maureen Green Foundation, the Wildlife Conservation Society, Australian 60 Minutes, Bruce Ludwig, Frank Levinson, and Cindy Calderon. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.