Parasites reduce territorial behaviour in red grouse (Lagopus lagopus scoticus)

Abstract

Hypotheses for the cause of population cycles have focused on the role of intrinsic mechanisms such as spacing behaviour and extrinsic mechanisms such as parasitism and predation. This paper examines the interaction between the two dominant hypotheses in the cycles of red grouse, parasitism and spacing behaviour. The influence of the caecal nematode, Trichostrongylus tenuis, on male aggressiveness was investigated using two approaches. First, the territorial behaviour of a group of male grouse experimentally treated with an anthelmintic to reduce parasite intensities was compared with a control group with natural intensities of infection. Second, the response of treated and control males to a novel conspecific territorial intruder were recorded using playback tests. Treated males, with reduced levels of parasitism, won significantly more territorial contests than control males and produced more aggressive behaviour in response to the playback recordings. These results show that parasite removal enhanced aggressive behaviour. Implications of these results on red grouse population dynamics are discussed.

Interactions between population processes in a cyclic species: parasites reduce autumn territorial behaviour of male red grouse

“…We found relatively similar treatment effects on flight call rate: dosed old males tended to perform more flight calls than challenged old males, while the reverse tendency was observed in young males. This result for old males was consistent with a previous experiment showing that parasite removal enhances flight call rate in spring (Fox and Hudson 2001). Ground calls are typical aggressive calls, so the observation that parasites limit ground call rate, and particularly in old males, was consistent with the initial hypothesis.…”

“…In this study, we focus on the effect of parasite intensity on testosterone-dependent territorial behaviour. Previous work has shown that parasites reduce aspects of red grouse sexual and aggressive behaviour in spring: males cleared of their nematode parasites performed more flight calls and won more territorial contests than control males (Fox and Hudson 2001). However, worm intensities are usually higher in autumn than in spring (e.g.…”

Broad-Scale Assessment of Rangeland Health, Grand Staircase–Escalante National Monument, USA

“…Fox and Hudson (2001) found that cecal nematodes (Trichostrongylus tenuis) could impact territoriality in red grouse. The louping ill virus, which is transmitted by the tick Ixodes ricinus from sheep to red grouse can result in lower densities, higher mortality, and reduced harvest .…”

Mounting an immune response correlates with decreased androgen levels in male peafowl, Pavo cristatus

“…A meta-analysis of these studies showed that the evidence for androgen-induced immunosuppression is ambiguous for birds (Roberts et al 2004). Fewer studies have taken into account that infections might have a suppressive effect on the expression of social and reproductive behavior via an effect of the immune system on the hypothalamus pituitary axis (see Hart 1990;Hillgarth and Wingfield 1997;Fox and Hudson 2001). That such an alternative pathway exists is suggested by a study in which male house finches, Carpodacus mexicanus, infected with coccidian parasites were found to have lower levels of testosterone than uninfected males (Duckworth et al 2001).…”