Predation on Moose Calves by European Brown Bears

Abstract: In North America, brown bears (Ursus arctos) can be a significant predator on moose (Alces alces) calves. Our study in Sweden is the first in which brown bears are the only predator on moose calves. Bears and moose occurred at densities of about 30/1,000 km² and 920/1,000 km², respectively, and bears killed about 26% of the calves. Ninety-two percent of the predation took place when calves were <1 month old. Bear predation was probably additive to other natural mortality, which was about 10% in areas both with and without bears. Females that lost their calves in spring produced more calves the following year (1.54 calves/F) than females that kept their calves (1.11 calves/F), which reduced the net loss of calves due to predation to about 22%.     

Increasing ocean temperature reduces the metabolic performance and swimming ability of coral reef damselfishes

Tropical coral reef teleosts are exclusively ectotherms and their capacity for physical and physiological performance is therefore directly influenced by ambient temperature. This study examined the effect of increased water temperature to 3 °C above ambient on the swimming and metabolic performance of 10 species of damselfishes (Pomacentridae) representing evolutionary lineages from two subfamilies and four genera. Five distinct performance measures were tested: (a) maximum swimming speed (U_crit), (b) gait‐transition speed (the speed at which they change from strictly pectoral to pectoral‐and‐caudal swimming, U_p?c), (c) maximum aerobic metabolic rate (MO_2?MAX), (d) resting metabolic rate (MO_2?REST), and (e) aerobic scope (ratio of MO_2?MAX to MO_2?REST, A_SC). Relative to the control (29 °C), increased temperature (32 °C) had a significant negative effect across all performance measures examined, with the magnitude of the effect varying greatly among closely related species and genera. Specifically, five species spanning three genera (Dascyllus, Neopomacentrus and Pomacentrus) showed severe reductions in swimming performance with U_crit reduced in these species by 21.3–27.9% and U_p?c by 32.6–51.3%. Furthermore, five species spanning all four genera showed significant reductions in metabolic performance with aerobic scope reduced by 24.3–64.9%. Comparisons of remaining performance capacities with field conditions indicate that 32 °C water temperatures will leave multiple species with less swimming capacity than required to overcome the water flows commonly found in their respective coral reef habitats. Consequently, unless adaptation is possible, significant loss of species may occur if ocean warming of ≥3 °C arises.     

Blow fly responses to semiochemicals produced by decaying carcasses

Volatiles from mouse carcasses in decay stages ranging from fresh to 33 days old were used to investigate oriented flight and landings in male and female blow flies of Calliphora vicina Robineau‐Desvoidy (Diptera: Calliphoridae). Oriented flight increased significantly from 36% towards fresh carcasses to 68%, 61% and 65% towards carcasses aged 3 days, 6 days and 9 days, respectively. Carcasses aged 20 days and 33 days were significantly less attractive, achieving 51% and 41% attraction, respectively. No differences emerged between the sexes in oriented flight, but a significant increase in female landings at the most attractive carcasses was observed. Headspace collections from the different stages of decay showed a succession in the volatile profile emitted from the carcasses and identified nine chemicals which peak in quantity in concurrence with the most attractive stages of decay. Three of these chemicals also showed dose–response effects as indicated by a significant correlation between the amount present and the proportion of flies responding. Blow flies are important pests and efficient traps are needed. The significant interaction between fly sex and carcass age highlights behavioural differences between male and female blow flies which can be exploited in blow fly trapping. Three new volatile chemicals, butylated hydroxyl toluene, 3‐hydroxy‐2‐butanone and nonanal, emitted from dead mice are suggested as potential attractants.     

Adaptation to Hypoxia by Increased HbO<Subscript>2</Subscript> Affinity and Decreased Red Cell ATP Concentration

THERE is a decrease in the O₂ affinity of mammalian haemoglobin (Hb) as the levels of 2,3-DPG or ATP are increased, which is explained by an allosteric effect on the HbO₂ binding^1,2. Similar observations on amphibians³ and fish⁴, which have molar ratios of ATP to Hb similar to those of DPG to Hb in mammals, suggest that red cell organic phosphates modulate Hb function in all vertebrates. The adaptation of mammals to various hypoxic stresses involves reduced HbO₂ affinity^5–9, the attendant increase in O₂ “unloading” capacity being mediated by an increase in the concentration of red cell 2,3-DPG. We have found the opposite response in hypoxic fish and suggest that an increased O₂ affinity results in increased O₂ transport for the fish.