Journal of Animal Ecology最新文献

Maternal age can influence reproductive success and offspring fitness, but the timing, magnitude and direction of those impacts are not well understood. Evolutionary theory predicts that selection on fertility senescence is stronger than maternal effect senescence, and therefore, the rate of maternal effect senescence will be faster than fertility senescence. We used a 36-year study of northern elephant seals (Mirounga angustirostris) to investigate reproductive senescence. Our dataset included 103,746 sightings of 1203 known-age female northern elephant seals. We hypothesized that fertility (maternal reproductive success), offspring survival and recruitment into the breeding population, and male offspring production would decline with advanced maternal age. Furthermore, we hypothesized that older females would shorten their moulting haul out to allow for more time spent foraging. We found evidence for both fertility and maternal effect senescence, but no evidence for senescence impacting offspring recruitment or sex ratio. Breeding probability declined from 96.4% (95% CI: 94.8%-97.5%) at 11 years old to 89.7% (81.9%-94.3%) at 19 years old, and the probability of offspring survival declined from 30.3% (23.6%-38.0%) at 11 years old to 9.1% (3.2%-22.9%) at 19 years old. The rates of decline for fertility and maternal effect senescence were not different from each other. However, maternal effect senescence had a substantially greater impact on the number of offspring surviving to age 1 compared to fertility senescence. Compared to a hypothetical non-senescent population, maternal effect senescence resulted in 5.3% fewer surviving pups, whereas fertility senescence resulted in only 0.3% fewer pups produced per year. These results are consistent with evolutionary theory predicting weaker selection on maternal effect than fertility senescence. Maternal effect senescence may therefore be more influential on population dynamics than fertility senescence in some systems.

Animal waste can contribute substantially to nutrient cycling and ecosystem productivity in many environments. However, little is known of the biogeochemical impact of animal excretion in wetland habitats. Here we investigate the effects of wood frog (Lithobates sylvaticus) tadpole aggregations on nutrient recycling, microbial metabolism and carbon cycling in geographically isolated wetlands. We used a paired mesocosm and field study approach that utilized measurements of tadpole excretion rates, microbial extracellular enzyme activities, and litter degradation. We found a strong relationship between tadpole development and nutrient excretion, demonstrating that ontological changes impact tadpole-mediated nutrient cycling in wetland habitats. Further, the interplay between population-level tadpole excretion and wetland hydrologic conditions increased ambient ${\mathrm{NH}}_4^{+}$ and ${\mathrm{PO}}_4^{3-}$ concentrations by 56 and 14 times, respectively, compared to adjacent wetlands without tadpoles. Within our mesocosm study, microbes decreased extracellular enzyme production associated with nitrogen acquisition in response to the presence of tadpole-derived nitrogen. In addition to microbial metabolic responses, tadpole presence enhanced litter breakdown in both mesocosms and wetlands by 7% and 12%, respectively, in comparison to reference conditions. These results provide evidence for the functional and biogeochemical role of tadpole aggregations in wetland habitats, with important implications for ecosystem processes, biodiversity conservation, and ecosystem management.

Research Highlight: Shiratsuru, S., & Pauli, J. N. (2024). Food-safety trade-offs drive dynamic behavioural antipredator responses among snowshoe hares. Journal of Animal Ecology, DOI: 10.1111/1365-2656.14183. Predation-risk effects are known to be context dependent, with impacts of perceived predation threat on individual antipredator responses, prey population demography, species interactions and community organization hinging on traits of the prey, the predator(s) and setting of the interaction. Yet, few empirical studies to date have simultaneously explored how these three drivers shape contingency in antipredator behaviour, the key first step in the process by which predation-risk effects play out, especially in free-living vertebrates. In a new study, Shiratsuru & Pauli (2024) address this knowledge deficit by showing that snowshoe hares (Lepus americanus) trade foraging for anti-predator vigilance dynamically as a function of winter food availability (a proxy for individual energetic state), the timing and intensity of predator activity, and environmental properties associated with elevated vulnerability to predator-induced mortality, notably including coat colour mismatch caused by variation in snow cover. These results offer new insight into the complexity of predation-risk effects and should serve as a guide for research aiming to better understand the expression of these effects under varying circumstances.