Wildlife and Landscape Science News

Wildlife Populations

> Mountain Juncos Adapt Breeding Strategies to Habitat

A five-year study in the Canadian Rocky Mountains examined variation in the life-history strategies of juncos between low- and high-elevation sites. A study by Heather Bears, supervised by Kathy Martin, demonstrated adaptive changes in certain life-history traits. Juncos at higher elevations adapted to a shorter breeding season by producing fewer offspring with higher annual survival.

The dark-eyed junco (Junco hyemalis) was monitored at the elevation extremes of its breeding range in Jasper National Park (Alberta). The study focussed on fitness-related traits – egg-laying schedules, reproductive success, offspring survival rates, and indicators of competitiveness such as body size and arrival time. The high-elevation birds were not lesser competitors (i.e., not likely excluded from low-elevation breeding sites).

High-elevation birds delayed egg-laying and reduced their breeding season to less than half that of low-elevation birds. This resulted in less broods per season. The high-elevation birds had 55-61% lower annual reproduction, a disadvantage that was offset by 15-20% higher offspring and adult survival. Overall, the study demonstrated that as elevation increases, alpine songbirds adopt a slower lifestyle producing fewer offspring each year but living longer and thus having more years to reproduce.

This project was carried out in collaboration with the Centre for Applied Conservation Research (University of British Columbia).

Results were profiled in Nature Research Highlights (Biology: Mile-high strategies) and published in the Journal of Animal Ecology:

Bears, H., K. Martin and G.C. White. 2009. Breeding in high-elevation habitat results in shift to slower life-history strategy within a single species. Journal of Animal Ecology 78(2): 365-375. [doi: 10.1111/j.1365-2656.2008.01491.x available via http://dx.doi.org]

Contact: Dr. Kathy Martin (604) 940-4667 or Heather Bears (778) 998-4384

> Polar Bear Diets in a Changing Arctic Ecosystem

A 30-year study suggests polar bears with specialized diets may be most vulnerable to sea-ice condition changes:

An ecosystem-based study on 1,738 individual bears across the Canadian Arctic shows that polar bears can alter foraging to take advantage of locally abundant prey, or to some degree compensate for reduced prey species, where they are not dependent on seal availability. Recent population data suggest highest vulnerability among polar bears with the most specialized diets.

Results were published in the journal, Ecological Monographs:

Thiemann, G.W., S.J. Iverson and I. Stirling. 2008. Polar bear diets and arctic marine food webs: insights from fatty acid analysis. Ecological Monographs 78(4): 591-613.

Newly recorded negative effects of climate warming in the southern Beaufort Sea:

Observations from 2003 to 2006 in this region suggest that polar bears were nutritionally stressed. A possible ecological explanation is the seal population downturn. A more likely cause is record amounts and duration of open water resulting in major changes in the sea-ice and marine environment, possibly influenced by climate warming.

Results were published in the journal, Arctic:

Stirling, I., E. Richardson, G.W. Thiemann and A.E. Derocher. 2008. Unusual predation attempts of polar bears on ringed seals in the southern Beaufort Sea: Possible significance of changing spring ice conditions. Arctic 61: 14-22.

Berries may offer little energy benefit for fasting polar bears:

The changing Arctic climate heightens the importance of whether polar bears can supplement stored fat reserves with terrestrial berries. The authors describe their analysis of breath CO₂ for stable carbon isotope (δ¹³C) values from 300 bears fasting on land in western Hudson Bay during open-water seasons. Results suggest bears that fed on berries received an insignificant amount of energetic benefit.

Results were published in the Canadian Journal of Zoology:

Hobson, K.A., I. Stirling and D.S. Andriashek. 2009. Isotopic homogeneity of breath CO2 from fasting and berry-eating polar bears: Implications for tracing reliance on terrestrial foods in a changing Arctic. Canadian Journal of Zoology 87: 50-55.

Contact: Dr. Ian Stirling (780) 435-7349

> Why Are Salmon Eggs Red?

The characteristic red colour of salmon eggs is due to carotenoids provided by the mother. In a recent study of wild and domestic salmon, significant links were demonstrated to support a hypothesis that this pigmentation improves offspring survival rate during incubation and supports disease resistance after hatching.

The study, a collaboration between Robert Letcher and Dan Heath at the Great Lakes Institute for Environmental Research (University of Windsor), sought correlations among carotenoid levels and incubation survival and disease resistance, specifically vibriosis. Carotenoids are naturally occuring organic pigments in plants and animals. They are consumed as part of the wild salmon diet. Domestic fish consume the carotenoid astaxanthin as an additive in their feed. The study included eggs of Chinook salmon (Oncorhynchus tshawytscha) from wild fish in the Quinsam and Chehalis rivers (British Columbia), and domestic fish from Vancouver Island.

The focus was on carotenoid levels in eggs reared as maternal families. Incubation survival and disease resistance were linked with mean carotenoid concentration measured in eggs within families. Egg carotenoid concentration was linked with specific disease resistance, in incubation and seven months later in life. The incubation-survival relationship was limited, however, suggesting a “threshold effect” of carotenoids on survival.

Results were published in the journal, Evolutionary Ecology Research:

Tyndale, S.T., R.J. Letcher, J. Heath and D.D. Heath. 2008. Why are salmon eggs red? Egg carotenoids and early life survival of chinook salmon (Oncorhynchus tshawytscha). Evolutionary Ecology Research 10(8): 1187-1199.

Contact: Dr. Robert Letcher (613) 998-6696

Health Effects of Toxics

> Metal Mining Effluent Regulations: Amendments to Fathead Minnow Toxicity Test Method

Environment Canada’s Method Development and Applications Unit has published amendments for EPS 1/RM/22 Test of Larval Growth and Survival Using Fathead Minnows (originally published in February 1992; amended November 1997). The most significant change to this method includes the requirement of regression statistics for quantitative data analysis and endpoint generation, and the change to a biomass sublethal endpoint. Other minor changes include technical and terminology clarifications.

This standardized test method is required under the Fisheries Act for the Metal Mining Effluent Regulations. The amended version of this method came into effect for the Environmental Effects Monitoring program (Metal Mining) in February 2009. A four-month period from November 2008 to February 2009 allowed preparation time for private toxicology laboratories to revise their in-house Standard Operating Procedures and for staff training on the changes to the test methodology.

The method is available for download from the Biological Methods Publications website.

Contact: Dr. Lisa Taylor (613) 991-4062

> Effects of Flame Retardants on Gene Expression in Chicken Cultures

A study, led by Sean Kennedy and Doug Crump, highlights the effects of two brominated flame retardants on gene expression in an avian species. Hexabromocyclododecane (HBCD) and polybrominated diphenyl ethers (PBDEs) are additive flame retardants used in a wide range of consumer products. Both compounds have been detected in free-living birds.

The study, conducted at the National Wildlife Research Centre (Ottawa), yielded results suggesting several key gene targets associated with xenobiotic metabolism, thyroid hormone (TH) transport and lipid metabolism were more responsive to HBCD than to PBDEs. An in vitro approach using hepatocytes derived from livers of embryonic chickens demonstrated the efficacy of using cell culture as a means to compare the relative potencies of different priority chemicals.

Concentration-dependent effects of two flame retardants (HBCD and the commercial penta-brominated diphenyl ether mixture DE-71) on cytotoxicity (toxic at the cellular level) and mRNA expression (process where genetic information is converted into a protein) were compared. The results overall indicate that, in cultured avian hepatocytes, xenobiotic-metabolizing enzymes and genes associated with the TH pathway and lipid regulation are vulnerable to these flame retardants and might be useful molecular markers of exposure.

Currently, toxicological and molecular end points of exposure are limited and this work may provide an approach to screen chemicals in avian species as part of the environmental regulatory process.

Results were published in the journal, Toxicological Sciences:

Crump, D., S. Chiu, C. Egloff and S.W. Kennedy. 2008. Effects of hexabromocyclododecane and polybrominated diphenyl ethers on mRNA expression in chicken (Gallus domesticus) hepatocytes. Toxicol. Sci. 106(2): 479-487.

Contact: Doug Crump (613) 998-7383