Animal Ecology (animal + ecology)

Distribution by Scientific Domains


Selected Abstracts


Density-dependent growth of young-of-the-year Atlantic salmon (Salmo salar) revisited

ECOLOGY OF FRESHWATER FISH, Issue 1 2010
I. Imre
Imre I, Grant JWA, Cunjak RA. Density-dependent growth of young-of-the-year Atlantic salmon (Salmo salar) revisited. Ecology of Freshwater Fish 2010: 19: 1,6. © 2009 John Wiley & Sons A/S Abstract,,, The length of individual young-of-the-year (YOY) Atlantic salmon (Salmo salar) in Catamaran Brook decreases with increasing population density following a negative power curve. Because most of this decrease in growth rate occurs at low densities (<1 fish·m,2), (Imre et al. 2005; Journal of Animal Ecology, 74: 508,516) suggested that exploitation competition for drifting prey rather than space limitation might be responsible for this pattern. Recently, (Ward et al. 2007; Journal of Animal Ecology, 76: 135,138) showed that the negative power curve of growth rate versus density can be caused by other mechanisms and suggested that Imre et al.'s evidence for density-dependent growth would have been stronger if we had analysed final size versus initial density rather than final density. We examined (i) whether the negative power curve of size versus density was also apparent in an analysis of final size versus initial density and tested two predictions that emerge from Ward et al.'s model, (ii) the variance in body size increases with population density, and (iii) the maximum fish size at a site is density-independent. The final size of YOY salmon decreased with increasing initial density following a negative power curve. Our data did not provide strong support for the above predictions emerging from Ward et al.'s model. Our analyses of different years, sites and seasons were consistent with the hypothesis of density-dependent growth of YOY salmon. [source]


IN FOCUS: Partial migration in tropical birds: the frontier of movement ecology

JOURNAL OF ANIMAL ECOLOGY, Issue 5 2010
Cagan H. Sekercioglu
A. E. Jahn, D. J. Levey, J. A. Hostetler & A. M. Mamani (2010) Determinants of partial bird migration in the Amazon Basin. Journal of Animal Ecology, 79, 983,992. Partial migration, in which only some individuals of a species migrate, might be central to the evolution of migratory behaviour and is likely to represent an evolutionary transition between sedentariness and complete migration. In one of the few detailed, individual-based migration studies of tropical birds, Jahn et al. study the partial migration system of a South American bird species for the first time. Food limitation forces the large adult males and small, young females to migrate, contrary to the expectations of the body size and dominance hypotheses. This study confirms the importance of food variability as the primary driver of migratory behaviour. There is urgent need for similar studies on the movement ecology of understudied tropical bird species, whose diversity of migratory behaviour can shed light on the evolution of bird migration. [source]


Safety in numbers: extinction arising from predator-driven Allee effects

JOURNAL OF ANIMAL ECOLOGY, Issue 3 2010
Stephen D. Gregory
A.M. Kramer & J.M. Drake (2010) Experimental demonstration of population extinction due to a predator-driven Allee effect. Journal of Animal Ecology, 79, 633,639. Experimental evidence of extinction via an Allee effect (AE) is a priority as more species become threatened by human activity. Kramer & Drake (2010) begin the International Year of Biodiversity with the important , but double-edged , demonstration that predators can induce an AE in their prey. The good news is that their experiments help bridge the knowledge gap between theoretical and empirical AEs. The bad news is that this predator-driven AE precipitates the prey extinction via a demographic AE. Although their findings will be sensitive to departures from their experimental protocol, this link between predation and population extinction could have important consequences for many prey species. [source]


Transgenerational immune priming as cryptic parental care

JOURNAL OF ANIMAL ECOLOGY, Issue 2 2010
Jukka Jokela
O. Roth, G. Joop, H. Eggert, J. Hilbert, J. Daniel, P. Schmid-Hempel & J. Kurtz (2009) Paternally derived immune priming for offspring in the red flour beetle, Tribolium castaneum. Journal of Animal Ecology, 79, 403,413. Eggs are relatively large and can provide offspring with resources that improve their survival. While such maternal effects are common, it has been difficult to imagine what, other than genes, individual offspring could receive from their fathers. The study byRoth et al. (2009a)suggests that we should look more closely. Their experiments show that red flour beetle fathers can transfer specific biochemical information to their offspring, priming their immune system to combat pathogens better. When mothers do the same, the offspring get a double dose of protection. This discovery alerts us to re-evaluate the importance of cryptic parental care. [source]


Environmental variance, population growth and evolution

JOURNAL OF ANIMAL ECOLOGY, Issue 1 2010
Shripad Tuljapurkar
N. Jonzén, T. Pople, K. Knape & M. Skjöld (2009) Stochastic demography and population dynamics in the red kangaroo (Macropus rufus). Journal of Animal Ecology, 79, 109,116. Environmental fluctuations on time scales of one to tens of generations are increasingly recognized as important determinants of population dynamics and microevolution. Jonzén et al. in this issue analyse how the vital rates of red kangaroos depend on annual rainfall, and estimate the elasticities of stochastic growth rate to the means and variances of the vital rates, as well as to the mean and variance of rainfall. Their results demonstrate how ecological and evolutionary studies can benefit from including explicit environmental drivers when modelling populations, and from the use of mean and variance elasticities. [source]


The physiology of predator stress in free-ranging prey

JOURNAL OF ANIMAL ECOLOGY, Issue 6 2009
Evan L. Preisser
M.J. Sheriff, C.J. Krebs & R. Boonstra (2009) The sensitive hare: sublethal effects of predator stress on reproduction in snowshoe hares. Journal of Animal Ecology, 78, 1249,1258. Ecologists have only begun to understand the physiological mechanisms underlying individual- and population-level responses of prey- to predator-related stress. Sheriff, Krebs and Boonstra advance this field by providing evidence that predator-induced increases in glucorticoid concentrations in wild female snowshoe hares (Lepus americanus) impact both litter size and offspring condition. They hypothesize that the glucocorticoid-mediated effects on reproduction provides an adaptive benefit: mothers ,programming' their offspring to be timid and risk-averse in high-risk environments should increase their survival probability. This research illuminates the connection between stress physiology and population-level changes and demonstrates the surprisingly far-reaching impact of predation risk. [source]


Density dependence hypotheses and the distribution of fecundity

JOURNAL OF ANIMAL ECOLOGY, Issue 2 2008
Miguel Ferrer
Summary 1Beja & Palma (2008, Journal of Animal Ecology, 77, doi: 10.1111/j.1365-2656.2007.01312.x) attempt to provide a critical analysis of the effectiveness and limitations of a previously published method (Ferrer et al. 2006, Journal of Animal Ecology, 75, 111,117.) to discriminate between Habitat Heterogeneity Hypothesis and the Individual Adjustment Hypothesis using real data from a Bonelli's eagle Hieraaetus fasciatus population. 2They conclude that significant and strong correlations between mean and CV or skewness are expected under a biologically plausible assumption about brood size distribution, and that the two hypotheses cannot therefore be distinguished. 3A major concern we have with their paper centres on this biologically plausible brood-size distribution. They used the same quasi-Poisson distribution of brood sizes (typical for a saturate population under Habitat Heterogeneity Hypothesis) for both families of simulations. So, is not surprising that both groups gave similar results. 4They argued that this approach was ,empirical', free of theoretical assumptions. But in testing between hypotheses, what we are looking for is precisely the differences among theoretical brood-size distributions predicted under the two hypotheses. 5Summarizing, with the same mean fecundity at high densities, both hypotheses must have different brood-size distributions. So the use of a single left-skewed distribution, typical of a real saturated population (most likely under Habitat Heterogeneity Hypothesis) in attempts to distinguish between the two hypotheses by re-sampling several times on the same left-skewed distribution, as done by Beja & Palma, is clearly inappropriate. [source]


Isotopic ecology ten years after a call for more laboratory experiments

BIOLOGICAL REVIEWS, Issue 1 2009
Carlos Martínez del Rio
Abstract About 10 years ago, reviews of the use of stable isotopes in animal ecology predicted explosive growth in this field and called for laboratory experiments to provide a mechanistic foundation to this growth. They identified four major areas of inquiry: (1) the dynamics of isotopic incorporation, (2) mixing models, (3) the problem of routing, and (4) trophic discrimination factors. Because these areas remain central to isotopic ecology, we use them as organising foci to review the experimental results that isotopic ecologists have collected in the intervening 10 years since the call for laboratory experiments. We also review the models that have been built to explain and organise experimental results in these areas. [source]