We investigated the impact of different fluorescent marking powders on both survivorship and daily body condition, measured as mass/volume ratio, using adult mountain pine beetles, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae), in a laboratory study. Initial condition of the marked beetle groups did not differ from that of an unmarked group. However, beetles in better initial condition survived longer, thus validating our condition index. The condition but not the survivorship of mountain pine beetles was affected by the marking treatment. Overall, the condition of beetles declined over time. The condition of marked beetles decreased at a higher rate than that of unmarked beetles while alive but at a lower rate after death. This pattern of decreasing condition suggests that marked beetles lost water faster than unmarked beetles while alive, so unmarked beetles had more water to lose after death. Because reduced condition may affect optimal dispersal behaviour, we suggest that these effects be routinely examined and minimized in mark-recapture studies.Résumé-Nous avons étudié l'impact de poudres fluorescentes de marquage sur la survie et sur la condition journalière, mesurée par le rapport masse/volume (mg/mm 3 ), dans une étude en laboratoire de dendroctones du pin ponderosa, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae). La condition initiale des coléoptères est semblable dans les groupes marqués et non marqués. Cependant, les coléoptères en meilleure condition initiale survivent plus longtemps, ce qui confirme la validité de notre indice de condition. Le marquage affecte la condition, mais non la survie, des dendroctones du pin ponderosa. Globalement, la condition des coléoptères diminue avec le temps. La condition des coléoptères marqués décline plus rapidement que celle des coléoptères non marqués durant leur vie; après la mort, leur taux de déclin est plus lent. Ce patron de déclin de la condition laisse croire que les coléoptères marqués perdent de l'eau plus rapidement que les non marqués durant leur vie, si bien qu'après la mort, les coléoptères non marqués ont plus d'eau à perdre. Parce qu'une condition inférieure peut affecter le comportement optimal de dispersion, nous suggérons d'examiner systématiquement ces effets et de les minimiser dans les études de marquage et de recapture.[Traduit par la Rédaction] Reid and Reid 588
We propose that changes in movement behavior may be a proximate mechanism that in�uences the accumulation of animals at habitat edges. We tested this idea with a combination of empirical and simulation experiments in a resource-free landscape. e movements of individual �our beetles, Tribolium confusum, were tracked across a paper arena edged with invisible tape until beetles crossed the edge. Movement behavior (step lengths and turn angles) and cumulative occupancy were analyzed according to distance from the edge. We found that beetles took smaller steps with larger turn angles near edges than in the center of the arena and that beetle distribution was highly biased towards the edge of the arena. We then tested two agent-based simulation models for each beetle: an edge-independent model and an edge-dependent model. Both models predicted less time spent at the edge than was observed. e proportion of time spent at edges depended on the propensity to cross the edge, which could not be explained by beetle body size or energetic condition. e distribution of animals with respect to habitat edges depends on many factors, but we suggest that proximate mechanisms such as movement behavior should be explicitly considered when interpreting animal distributions.
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