TY - JOUR

T1 - Rats dying for mice: Modelling the competitor release effect

AU - Caut, Stephan

AU - Casanovas, Jorge G.

AU - Virgos, E.

AU - Lozano Mendoza, Jorge

AU - Witmer, G.W.

AU - Courchamp, F.

PY - 2007/12/1

Y1 - 2007/12/1

N2 - Introduced vertebrate predators are one of the most important threats to endemic species throughout a range of ecosystems, in particular on islands in biodiversity hot spots. Consequently, the reduction of predator numbers is considered a key conservation action in the management of many native vertebrates vulnerable to predators. It is now established that control attempts may affect non-target species through trophic interactions, but little is known concerning their consequences on competitive relationships. We study a mathematical model mimicking the effects of controlling introduced species in the presence of their competitors. We used two competing rodents to illustrate our study: black rats, Rattus rattus, and mice, Mus musculus. Analyses of the model show that control of only one introduced species logically results in the dramatic increase of the overlooked competitor. We present empirical data that confirm our theoretical predictions. Less intuitively, this process, which we term 'the competitor release effect', may also occur when both introduced competitors are simultaneously controlled. In our setting, controlling both predators can promote their coexistence. This occurs as soon as the inferior competitor benefits from the differential effect of the simultaneous control of both competitors, that is, when the indirect positive effect of control (the removal of their competitors) exceeds its direct negative effect (their own removal). Both control levels and target specificity have a direct influence on the extent of this process: counter-intuitively, the stronger and more specific the control, the greater the effect. The theoretical validation of the competitor release effect has important implications in conservation, especially for control management.

AB - Introduced vertebrate predators are one of the most important threats to endemic species throughout a range of ecosystems, in particular on islands in biodiversity hot spots. Consequently, the reduction of predator numbers is considered a key conservation action in the management of many native vertebrates vulnerable to predators. It is now established that control attempts may affect non-target species through trophic interactions, but little is known concerning their consequences on competitive relationships. We study a mathematical model mimicking the effects of controlling introduced species in the presence of their competitors. We used two competing rodents to illustrate our study: black rats, Rattus rattus, and mice, Mus musculus. Analyses of the model show that control of only one introduced species logically results in the dramatic increase of the overlooked competitor. We present empirical data that confirm our theoretical predictions. Less intuitively, this process, which we term 'the competitor release effect', may also occur when both introduced competitors are simultaneously controlled. In our setting, controlling both predators can promote their coexistence. This occurs as soon as the inferior competitor benefits from the differential effect of the simultaneous control of both competitors, that is, when the indirect positive effect of control (the removal of their competitors) exceeds its direct negative effect (their own removal). Both control levels and target specificity have a direct influence on the extent of this process: counter-intuitively, the stronger and more specific the control, the greater the effect. The theoretical validation of the competitor release effect has important implications in conservation, especially for control management.

KW - Alien predator control

KW - Biological invasion

KW - Competing rodent

KW - Control strategy

KW - Introduced mammal

KW - biodiversity

KW - biological invasion

KW - coexistence

KW - competition (ecology)

KW - introduced species

KW - nontarget organism

KW - numerical model

KW - predator

KW - rodent

KW - species conservation

KW - trophic interaction

KW - Mammalia

KW - Mus

KW - Mus musculus

KW - Rattus

KW - Rattus rattus

KW - Rodentia

KW - Vertebrata

KW - Sustainability Science

KW - Biology

UR - http://www.scopus.com/inward/record.url?scp=34247519410&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/22cdf3ca-cdde-312b-add1-65f85aad72e0/

U2 - 10.1111/j.1442-9993.2007.01770.x

DO - 10.1111/j.1442-9993.2007.01770.x

M3 - Journal articles

VL - 32

SP - 858

EP - 868

JO - Austral Ecology

JF - Austral Ecology

SN - 1442-9985

IS - 8

ER -