Recent Publications

53. Gorrell, J.C., A.G. McAdam, D. W. Coltman, M.M. Humphries, and S. Boutin. 2010. Adopting kin enhances inclusive fitness in asocial red squirrels. Nature Communications 1:22 doi: 10.1038/ncomms1022.

Tue, 1 Jun 2010 23:15:46 -0400

Media Coverage of this paper:
Jamie Gorrell interview on Quirks & Quarks with Bob McDonald, CBC, June 2010 (link)
Red Squirrels adopt abandoned pups. by Julianna Cummins, Edmonton Journal (link)

52. Dantzer, B., A. G. McAdam, R. Palme, Q. E. Fletcher, S. Boutin, M. M. Humphries, and R. Boonstra. 2010. Fecal cortisol metabolite levels in free-ranging North American red squirrels: Assay validation and the effects of reproductive condition. General and Comparative Endocrinology. 167: 279-286.

Sat, 29 May 2010 00:00:03 -0400

51. Larivée, M. L., S. Boutin, J. R. Speakman, A.G. McAdam, and M. M. Humphries. 2010. Associations between over-winter survival and resting metabolic rate in juvenile North American red squirrels (Tamiasciurus hudsonicus). Functional Ecology, 24: 597-607.

Wed, 20 Jan 2010 23:58:06 -0500

46. Guillemette, C. U., Q. E. Fletcher, S. Boutin, R. M. Hodges, A. G. McAdam, and M. M. Humphries. 2009. Lactating red squirrels experiencing high heat load occupy less insulated nests. Biology Letters 5: 166-168.

Mon, 23 Mar 2009 10:10:24 -0400

By measuring the insulative capacity of active red squirrel nests KRSP researchers were able to provide the first empirical test of the heat dissipation limit hypothesis in the wild. This hypothesis states that a female’s ability to provide nutrition for her pups might be limited by her ability to dissipate heat. Consistent with this hypothesis, KRSP researchers found that lactating red squirrels used less insulated nests under conditions of potentially high heat stress.

Murray Humphries was interviewed about this research on Quirks and Quarks (link).

45. Descamps, S., S. Boutin, A. G. McAdam, D. Berteaux, and J.-M. Gaillard. 2009. Survival costs of reproduction vary with age in North American red squirrels. Proceedings of the Royal Society of London, B. 276: 1129-1135.

Sun, 22 Mar 2009 10:35:30 -0400

Abstract
The costs of reproduction are expected to be higher under unfavourable conditions, so that breeding in years of low food supply should have important costs. In addition, the costs of reproduction may be contingent on the age of individuals, and young growing and old senescent individuals should suffer higher costs than the prime-age ones. We tested these predictions by investigating the costs of reproduction as a function of food availability and age in female North American red squirrels using the long-term data on survival and reproduction. We found that the costs of reproduction were independent of food supply, and we did not detect any trade-off between the current and future reproduction. We also did not detect any survival cost of reproduction for the prime-age females, but found evidence for survival costs in yearlings and old (6 years or above) females with successfully breeding individuals having a lower chance of survival compared with unsuccessful or non-breeding ones. These results supported our prediction that the costs of reproduction depended on the age of female red squirrels and were higher in young growing and old
senescent individuals. Our study also indicated that, in contrast to large herbivores, heterogeneity in individual quality and viability selection in red squirrels do not affect the study of trade-offs and of the age variation in life-history traits.

41.Boonstra, R., J. E. Lane, S. Boutin, A. Bradley, L. Desantis, A. E. M. Newman, and K. K. Soma. 2008. Plasma DHEA levels in wild, territorial red squirrels: Seasonal variation and effect of ACTH. General and Comparative Endocrinology, 158: 61-67.

Tue, 1 Apr 2008 11:23:46 -0400

Normally territorial behavior in mammals is limited to the breeding season and is tightly coupled to circulating gonadal steroid levels. In contrast, both male and female red squirrels also defend territories during the non-breeding season. A pro-hormone – dehydroepiandrosterone (DHEA) – produced by the adrenals has been linked to aggression. We found the levels are very high, particularly when red squirrels are not breeding and when density was high. Our study is the first examination this pro-hormone in a wild rodent and the first field experiment on the regulation of plasma DHEA in any wild mammal.

37. Boon, A. K., D. Reale, and S. Boutin. 2007. The interaction between personality, offspring fitness and food abundance in North American red squirrels. Ecology Letters 10: 1094-1104.

Sun, 16 Dec 2007 22:28:55 -0500

Red squirrels exhibit distinct personalities. A female’s activity influences the growth rates of her pups and her aggressiveness is related to the survival of her offspring over winter. These effects, however, change from one year to the next providing evidence for balancing selection that might maintain variation in personality in this population.

Listen to Adi Boon’s interview on Quirks and Quarks (www)

36. Descamps, S., S. Boutin, D. Berteaux, and J.-M. Gaillard. 2007. Female red squirrels fit Williams' hypothesis of increasing reproductive effort with increasing age. Journal of Animal Ecology 76: 1192-1201

Sat, 15 Dec 2007 22:20:02 -0500

Summary
1. Williams predicted that reproductive effort should increase as individuals age and their reproductive value declines. This simple prediction has proven difﬁcult to test because conventional measures of energy expenditure on reproduction may not be a true reﬂection of reproductive effort.

1. We investigated age-speciﬁc variation in female reproductive effort in a stable population of North American red squirrels where energy expenditure on reproduction is likely to reﬂect actual reproductive effort. We used seven measures of reproductive effort spanning conception to offspring weaning.

1. We found that females completed growth by age 3 and that reproductive value decreased after this age likely because of reproductive and survival senescence. We therefore, predicted that reproductive effort would increase from age 3 onwards.

1. The probability of breeding, litter mass at weaning, and likelihood of territory bequeathal were all lower for 1- and 2-year-old females than for females older than 3 years, the age at which growth is completed. That growing females are faced with additional energetic requirements might account for their lower allocation to reproduction as compared with older females.

1. The probability of attempting a second reproduction within the same breeding season and the propensity to bequeath the territory to juveniles increased from 3 years of age onwards, indicating an increase in reproductive effort with age. We think this increase in reproductive effort is an adaptive response of females to declining reproductive values when ageing, thereby supporting Williams’ prediction.

35. LaMontagne, J. L., and S. Boutin. 2007. Local-scale variability and synchrony in mast seeding of Picea glauca. Journal of Ecology 95: 991-1000.

Fri, 14 Dec 2007 21:41:12 -0500

1. Mast seeding is the synchronous and highly variable production of seed by a population of plants. Mast seeding results from the behaviour of individuals; however, little is known about the synchrony of individuals at local scales.

2. We address two primary questions at a within-population (17–36 ha study plots) and individual level: (i) How variable is seed production between and within years? (ii) How synchronized is seed production between individuals?

3. We monitored annual cone production of 356 Picea glauca (white spruce) from 1990 to 2005 within four plots spanning a total distance of 5.3 km in the Yukon Territory, Canada.

4. Spearman correlations (rs) were conducted to test for synchrony. Overall, the trees were moderately synchronous (mean rs (± SE) of 0.52 ± 0.14), and synchrony was statistically detectable (rs > 0) over all distances. Individuals < 75 m apart were highly synchronous (0.64 ± 0.18), and correlations dropped to 0.33 ± 0.07 for trees > 3 km apart. There was considerable variation in cone production patterns among pairs of individuals.

5. The number of mast years per plot varied from one to three. During a mast year, many individuals within plots produced large cone crops, with more variability between individuals in low mean cone years. Individual trees had dominant endogenous cycles varying from none to 1–5 years. Forty-four per cent of trees had no signiﬁcant lag, 23% a negative 1-year lag, and 20% a positive 3-year lag. Basal area did not inﬂuence lags, but trees with higher mean cone production throughout the study were more likely to have a 3-year lag compared with no lag.

6. The scale of highest synchrony coincided with the scale at which the dominant seed predator in the area, the territorial red squirrel (Tamiasciurus hudsonicus), operates. This may be the scale at which selection for synchrony occurs.

7 . Based on high synchrony locally, high synchrony within a mast year, and multiple lags in cone production by individuals, both available resources and strong weather cues appear to play roles in the observed patterns.

34. Kerr, T. D., S. Boutin, J. L. LaMontagne, A. G. McAdam, and M. M. Humphries. 2007. Persistent maternal effects on juvenile survival in North American red squirrels. Biology Letters 3: 289 - 291.

Wed, 12 Dec 2007 21:37:36 -0500

Abstract
Maternal effects can have lasting ﬁtness consequences for offspring, but these effects are often difﬁcult to disentangle from associated responses
in offspring traits. We studied persistent maternal effects on offspring survival in North American red squirrels (Tamiasciurus hudsonicus) by
manipulating maternal nutrition without altering the post-emergent nutritional environment experienced by offspring. This was accomplished by providing supplemental food to reproductive females over winter and during reproduction, but removing the supplemental food from the system
prior to juvenile emergence. We then monitored juvenile dispersal, settlement and survival from birth to 1 year of age. Juveniles from supplemented mothers experienced persistent and magnifying
survival advantages over juveniles from control mothers long after supplemental food was removed. These maternal effects on survival per-
sisted, despite no observable effect on traits normally associated with high offspring quality, such as body size, dispersal distance or territor y
quality. However, supplemented mothers did provide their juveniles an early start by breeding an average of 18 days earlier than control mothers,
which may explain the persistent survival advantages their juveniles experienced.