Conserving dryland lizards by reducing predator‐mediated apparent competition and direct competition with introduced rabbits

Conserving dryland lizards by reducing predator‐mediated apparent competition and direct... 1 Native skinks Oligosoma spp. in New Zealand’s dry grasslands have declined in range and abundance since the arrival of humans. I hypothesized that introduced rabbits Oryctolagus cuniculus exacerbate this decline by supporting introduced mammalian predators for which they are primary prey; by sudden declines in abundance that cause predators to switch to skinks; by grazing vegetation, thereby reducing skink refuges from predators; and by reducing skink food and shelter from climatic extremes. The first three effects cause enhanced skink predation and represent indirect or apparent competition. The fourth effect represents direct competition. 2 Interactions between two introduced predators (ferrets Mustela furo and cats Felis catus), rabbits and two secondary prey (McCann’s skink O. maccanni and common skink O. nigriplantare polychroma) were studied. By measuring skink consumption, and predator, rabbit and skink numbers, offtake of skinks by predators under varying rabbit and skink densities was calculated. 3 Predation by ferrets and cats was inversely density‐dependent because predation accelerated at low skink densities. As skink densities rose, predation became an increasingly less important source of mortality. Therefore, predation could potentially exterminate skink populations if densities fell below some critical range. 4 Predation of skinks increased markedly after sudden declines in rabbit abundance, because predators remained abundant but switched to feeding on skinks. Although a temporary effect, repeated cycles of intense rabbit control and population recovery may have chronic detrimental effects on skink population viability. 5 Optimal rabbit management for maintaining viable skink populations is likely to require avoidance of large swings in rabbit abundance by maintaining populations at low, stable levels. Fewer rabbits mean fewer predators and greater refuge (less apparent competition), and improved food and shelter (less direct competition). If large swings in rabbit abundance cannot be avoided, the effects of prey‐switching could be reduced by controlling predators when rabbit numbers decline. 6 Better understanding and management of primary–secondary prey systems, where the primary prey consume the habitat of secondary prey, will require recognition of the extra complexities that underlie these systems. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Ecology Wiley

Conserving dryland lizards by reducing predator‐mediated apparent competition and direct competition with introduced rabbits

Journal of Applied Ecology, Volume 38 (6) – Jan 1, 2001

Loading next page...
 
/lp/wiley/conserving-dryland-lizards-by-reducing-predator-mediated-apparent-RXPOXTpZj0
Publisher
Wiley
Copyright
Copyright © 2001 Wiley Subscription Services
ISSN
0021-8901
eISSN
1365-2664
DOI
10.1046/j.0021-8901.2001.00685.x
Publisher site
See Article on Publisher Site

Abstract

1 Native skinks Oligosoma spp. in New Zealand’s dry grasslands have declined in range and abundance since the arrival of humans. I hypothesized that introduced rabbits Oryctolagus cuniculus exacerbate this decline by supporting introduced mammalian predators for which they are primary prey; by sudden declines in abundance that cause predators to switch to skinks; by grazing vegetation, thereby reducing skink refuges from predators; and by reducing skink food and shelter from climatic extremes. The first three effects cause enhanced skink predation and represent indirect or apparent competition. The fourth effect represents direct competition. 2 Interactions between two introduced predators (ferrets Mustela furo and cats Felis catus), rabbits and two secondary prey (McCann’s skink O. maccanni and common skink O. nigriplantare polychroma) were studied. By measuring skink consumption, and predator, rabbit and skink numbers, offtake of skinks by predators under varying rabbit and skink densities was calculated. 3 Predation by ferrets and cats was inversely density‐dependent because predation accelerated at low skink densities. As skink densities rose, predation became an increasingly less important source of mortality. Therefore, predation could potentially exterminate skink populations if densities fell below some critical range. 4 Predation of skinks increased markedly after sudden declines in rabbit abundance, because predators remained abundant but switched to feeding on skinks. Although a temporary effect, repeated cycles of intense rabbit control and population recovery may have chronic detrimental effects on skink population viability. 5 Optimal rabbit management for maintaining viable skink populations is likely to require avoidance of large swings in rabbit abundance by maintaining populations at low, stable levels. Fewer rabbits mean fewer predators and greater refuge (less apparent competition), and improved food and shelter (less direct competition). If large swings in rabbit abundance cannot be avoided, the effects of prey‐switching could be reduced by controlling predators when rabbit numbers decline. 6 Better understanding and management of primary–secondary prey systems, where the primary prey consume the habitat of secondary prey, will require recognition of the extra complexities that underlie these systems.

Journal

Journal of Applied EcologyWiley

Published: Jan 1, 2001

Keywords: ; ; ; ; ;

References

  • Predation by introduced foxes on native bush rats in Australia: do foxes take the doomed surplus?
    Banks, P.B.
  • Setting thresholds for pest control: how does pest density affect resource viability?
    Choquenot, D.; Parkes, J.
  • Cats protecting birds: modelling the mesopredator release effect
    Courchamp, F.; Langlais, M.; Sugihara, G.
  • Refuge theory and biological control
    Hawkins, B.A.; Thomas, M.B.; Hochberg, M.E.
  • The impact of rabbit control on predator sightings in the semi‐arid high country of the South Island, New Zealand
    Norbury, G.; McGlinchy, A.
  • Control of a stoat (Mustela erminea) population irruption to enhance mohua (yellowhead) (Mohua ochrocephala) breeding success in New Zealand
    O’Donnell, C.F.J.; Dilks, P.J.; Elliott, G.P.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create folders to
organize your research

Export folders, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off