Maintenance of variable responses for coping with wetland drying in freshwater turtles

Aquatic animals inhabiting temporary wetlands must respond to habitat drying either by estivating or moving to other wetlands. Using radiotelemetry and capture mark recapture, we examined factors influencing the decisions made by individuals in a population of freshwater turtles (Chelodina longicollis) in response to wetland drying in southeastern Australia. Turtles exhibited both behaviors, either remaining quiescent in terrestrial habitats for variable lengths of time (terrestrial estivation) or moving to other wetlands. Both the proportion of individuals that estivated terrestrially and the time individuals spent in terrestrial habitats increased with decreasing wetland hydroperiod and increasing distance to the nearest permanent wetland, suggesting behavioral decisions are conditional or state dependent (i.e., plastic) and influenced by local and landscape factors. Variation in the strategy or tactic chosen also increased with increasing isolation from other wetlands, suggesting that individuals differentially weigh the costs and benefits of residing terrestrially vs. those of long-distance movement; movement to other wetlands was the near universal strategy chosen when only a short distance must be traveled to permanent wetlands. The quality of temporary wetlands relative to permanent wetlands at our study site varies considerably and unpredictably with annual rainfall and with it the cost-benefit ratio of each strategy or tactic. Residency in or near temporary wetlands is more successful during wet periods due to production benefits, but movement to permanent wetlands is more successful, or least costly, during dry periods due to survival and body condition benefits. This shifting balance may maintain diversity in response of turtles to the spatial and temporal pattern in wetland quality if their response is in part genetically determined.     

Observations on the nocturnal feeding of some mesopelagic decapod crustacea

Feeding in relation to temporal changes in the depth distribution of predator and prey is described for 9 species of mesopelagic decapods from an examination of 268 foreguts. Intensive nighttime feeding appears to be the rule in all species. The smaller decapods Sergestes (Sergestes) atlanticus, Sergestes (Sergestes) sargassi and Sergestes (Sergestes) pectinatus exploit the smaller prey, principally copepods and to a lesser extent ostracods. Larger decapod species Sergestes (Sergestes) henseni, Sergestes (Sergestes) curvatus, Sergestes (Sergia) grandis, Systellaspis debilis, and Acanthephyra purpurea mainly prey on macrozooplankton and micronekton, i.e., chaetognaths, euphausiids, decapods and fish, but copepods also occur in the foreguts. Gennadas valens is exceptional for the high incidence of foraminiferal remains, and a predator-prey relationship seems probable. All 9 decapod species have mixed diets, and pronounced feeding preferences are not evident. However, a high incidence of “secondary” feeding or “dietary contamination” has been deduced from the frequent occurrence of remains of the copepods Pleuromamma spp. and Oncaea spp. in the foreguts of the larger decapod species. Direct feeding cannot have occurred, since the depth distributions of these copepods and decapods are disjunct by day and night. It is concluded that the remains of Pleuromamma probably represent the food of the larger prey such as chaetognaths etc. which are eaten by the decapods. The presence of Oncaea is speculatively attributed to a possible ectoparasitic relationship with the larger prey items, but confirmatory evidence is required. These anomalies suggest that caution must be exercised in deducing predator-prey relationships simply from gut contents without consideration of distributional factors.     

Prevalence of sustainable and unsustainable use of wild species inferred from the IUCN Red List of Threatened Species

Unsustainable exploitation of wild species represents a serious threat to biodiversity and to the livelihoods of local communities and Indigenous peoples. However, managed, sustainable use has the potential to forestall extinctions, aid recovery, and meet human needs. We analyzed species-level data for 30,923 species from 13 taxonomic groups on the International Union for Conservation of Nature Red List of Threatened Species to investigate patterns of intentional biological resource use. Forty percent of species (10,098 of 25,009 species from 10 data-sufficient taxonomic groups) were used. The main purposes of use were pets, display animals, horticulture, and human consumption. Intentional use is currently contributing to elevated extinction risk for 28–29% of threatened or near threatened (NT) species (2752–2848 of 9753 species). Intentional use also affected 16% of all species used (1597–1631 of 10,098). However, 72% of used species (7291 of 10,098) were least concern, of which nearly half (3469) also had stable or improving population trends. The remainder were not documented as threatened by biological resource use, including at least 172 threatened or NT species with stable or improving populations. About one-third of species that had use documented as a threat had no targeted species management actions to directly address this threat. To improve use-related red-list data, we suggest small amendments to the relevant classification schemes and required supporting documentation. Our findings on the prevalence of sustainable and unsustainable use, and variation across taxa, can inform international policy making, including the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, the Convention on Biological Diversity, and the Convention on International Trade in Endangered Species.