Recent success in the conservation of many marine mammals has resulted in new management challenges due to increasing conflict with fisheries. Increasing predation by pinnipeds on threatened salmon ...is of particular concern. Seemingly, pinniped conservation is now in conflict with the recovery of threatened salmon, creating a dilemma for managers.
We use the Lower Columbia River as a case study for examining the relationship between seasonal California sea lion Zalophus californianus abundance and survival of threatened salmon. To quantify mortality associated with increasing sea lion abundance, we examined the effect of seasonal sea lion abundance on adult Chinook salmon Oncorhynchus tshawytscha survival during migrations through the Lower Columbia River. We integrated data on survival with data on population‐specific migration timing, allowing quantification of the relationship between sea lion abundance and survival in 18 populations of spring–summer Chinook salmon listed as Threatened or Endangered under the U.S. Endangered Species Act.
Of the 18 populations examined, earlier migrating populations experienced lower survival in association with increased exposure to higher sea lion abundance. We estimated that in years with high sea lion abundance, the nine earliest‐migrating populations experienced an additional 21.1% (95% CI = 16.3–26.1) mortality compared to years with baseline sea lion abundance, while the nine latest migrating populations experienced an additional 10.1% (7.5–13.0).
Synthesis and applications. Integrating datasets on seasonal survival and migration timing made it possible for us to estimate population‐specific mortality associated with increased sea lion abundance in the Lower Columbia River. This information could not be produced from any one dataset, highlighting the utility of data integration approaches. The mortality experienced by early migrating Chinook salmon suggests the potential for demographic and evolutionary consequences. Management actions such as hazing, relocating, or removing individuals that are frequent predators on salmon have been proposed. Identifying the management actions that will allow for socially and legally acceptable trade‐offs between multiple conservation and other social values will be facilitated by development of explicit multi‐species management frameworks. Continued monitoring will help to reduce the substantial uncertainty about the effect of pinnipeds on salmon and the predicted outcomes of alternative management actions.
Integrating datasets on seasonal survival and migration timing made it possible for us to estimate population‐specific mortality associated with increased sea lion abundance in the Lower Columbia River. This information could not be produced from any one dataset, highlighting the utility of data integration approaches. The mortality experienced by early migrating Chinook salmon suggests the potential for demographic and evolutionary consequences. Management actions such as hazing, relocating, or removing individuals that are frequent predators on salmon have been proposed. Identifying the management actions that will allow for socially and legally acceptable trade‐offs between multiple conservation and other social values will be facilitated by development of explicit multi‐species management frameworks. Continued monitoring will help to reduce the substantial uncertainty about the effect of pinnipeds on salmon and the predicted outcomes of alternative management actions.
The Rise of the Mesopredator Prugh, Laura R; Stoner, Chantal J; Epps, Clinton W ...
Bioscience,
10/2009, Letnik:
59, Številka:
9
Journal Article
Recenzirano
Apex predators have experienced catastrophic declines throughout the world as a result of human persecution and habitat loss. These collapses in top predator populations are commonly associated with ...dramatic increases in the abundance of smaller predators. Known as “mesopredator release,” this trophic interaction has been recorded across a range of communities and ecosystems. Mesopredator outbreaks often lead to declining prey populations, sometimes destabilizing communities and driving local extinctions. We present an overview of mesopredator release and illustrate how its underlying concepts can be used to improve predator management in an increasingly fragmented world. We also examine shifts in North American carnivore ranges during the past 200 years and show that 60% of mesopredator ranges have expanded, whereas all apex predator ranges have contracted. The need to understand how best to predict and manage mesopredator release is urgent—mesopredator outbreaks are causing high ecological, economic, and social costs around the world.
Phenology is an ecologically critical attribute that is commonly coordinated with other plant traits. Phenological shifts may be the result of evolutionary adjustments to persistently new conditions, ...or they may be transitory, varying with annual fluxes in abiotic conditions. In summer-dry, fire-prone Mediterranean-type climates, for example, many plant lineages have historically migrated from forests to more arid shrublands resulting in adaptive trait changes. These shifts in habitat abiotic conditions and biotic interactions influence morphology of flowers and fruits and interact with phenological timing. The Arbutoideae (Ericaceae) is one lineage that illustrates such modifications, with fruit characters evolving among genera from fleshy to dry fruit, thin to stony endocarps, and bird to rodent dispersal, among other changes. We scored herbarium collections and used ancestral trait analyses to determine phenological shifts among the five Arbutoid genera found in semi-arid climates. Our objective was to determine if phenology shifts with the phylogenetic transition to different reproductive characters. Our results indicate that phenological shifts began with some traits, like the development of a stony endocarp or dry fruits, but not with all significant trait changes. We conclude that early phenological shifts correlating with some reproductive traits were permissive for the transition to other later character changes.
Interactions among terrestrial carnivores involve a complex interplay of competition, predation and facilitation via carrion provisioning, and these negative and positive pathways may be closely ...linked. Here, we developed an integrative framework and synthesized data from 256 studies of intraguild predation, scavenging, kleptoparisitism and resource availability to examine global patterns of suppression and facilitation. Large carnivores were responsible for one third of mesocarnivore mortality (n = 1,581 individuals), and intraguild mortality rates were superadditive, increasing from 10.6% to 25.5% in systems with two vs. three large carnivores. Scavenged ungulates comprised 30% of mesocarnivore diets, with larger mesocarnivores relying most heavily on carrion. Large carnivores provided 1,351 kg of carrion per individual per year to scavengers, and this subsidy decreased at higher latitudes. However, reliance on carrion by mesocarnivores remained high, and abundance correlations among sympatric carnivores were more negative in these stressful, high‐latitude systems. Carrion provisioning by large carnivores may therefore enhance suppression rather than benefiting mesocarnivores. These findings highlight the synergistic effects of scavenging and predation risk in structuring carnivore communities, suggesting that the ecosystem service of mesocarnivore suppression provided by large carnivores is strong and not easily replaced by humans.
Interactions among terrestrial carnivores involve a complex interplay of competition, predation and facilitation via carrion provisioning, and these negative and positive pathways may be closely linked. We conducted a quantitative synthesis of scavenging and intraguild predation studies, and we found that large carnivores consistently suppressed populations of smaller carnivores despite providing substantial carrion subsidies. These findings highlight the synergistic effects of scavenging and predation risk in structuring carnivore communities, suggesting that the ecosystem service of mesocarnivore suppression provided by large carnivores is strong and not easily replaced by humans.
Breeding timing is one of the key life-history traits considered to be under strong stabilizing selection, such that offspring should be born when food resources are most abundant. Predation, ...however, may also affect the breeding timing because nest predation is a leading mortality for many species, although this possibility has been less considered. Here, we examined the possible effects of nest predation on breeding timing by comparing sympatric scops owls in a subtropical forest where only reptilian predators are present. The Japanese Scops Owl (Otus semitorques Temminck and Schlegel, 1844), a dietary generalist, bred one month earlier than the specialist Ryukyu Scops Owl (Otus elegans (Cassin, 1852)). The breeding timing of the Ryukyu Scops Owl matched with the emergence of their main prey species, but also matched with predator activity. Accordingly, the predation rate on eggs or nestlings was 7.5 times higher in the Ryukyu Scops Owl (13.9%; 21 out of 150 nests) than in the Japanese Scops Owl (1.9%; 1 out of 52 nests). Clutch size, on the other hand, was significantly larger in the Ryukyu Scops Owl than in the Japanese Scops Owl, possibly compensating loss from predation. Although alternative explanations still remain, our results suggest that the food generalist might have adjusted its breeding timing to avoid nest predation, whereas the breeding timing of the specialist might have been constrained by the availability of its main prey items.
The stomach of a spotted wolffish (Anarhichas minor) caught in Icelandic waters was found to contain ~727 greater eelpout larvae (Lycodes esmarkii). All the larvae were of similar size and at a ...similar state of digestion, indicating they were all consumed together. The likely explanation for this observation is that greater eelpout lay their eggs in a nest, with the larvae remaining in the nest for a short period after hatching. The larvae were then predated upon by the spotted wolffish while still in the nest. This study sheds new light on greater eelpout in Icelandic waters, with recently hatched larvae being present in March, breeding at a depth of ~200–250 m, and likely exhibiting nesting behavior, which has not previously been documented.
Many animal species protect their eggs against predators, and other species may profit from this by adding their eggs to those of the protecting species.
We studied two tiny species of predatory ...mites that share a food source, are engaged in intraguild predation, and which eggs are attacked by the same egg predator.
One of these predatory mites (Neoseiulus californicus) adds its eggs to those of the other species (Gynaeseius liturivorus) which guards its eggs from egg predators, resulting in reduced predation of the eggs of the nonguarding species. The guarding species experiences costs in the form of intraguild predation of her offspring, and the addition of eggs to the guarding species therefore qualifies as brood parasitism.
In the presence of egg predators, the brood parasite preferentially adds its eggs to those of the guarding host species, not to those of another, nonguarding mite species.
This cuckoo behaviour comes with a cost for the parasite when egg predators are absent, and therefore only occurs when egg predators are present.
Our findings emphasize the importance of the risk of egg predation as a factor driving facultative brood parasitism.
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