Jean Huot

Riparian forest strips as habitat for breeding birds in Boreal forests

Riparian forest strips are usually protected from logging for their buffer effect on aquatic habitats. However, their value to terrestrial wildlife is unknown. From 1989 to 1992, we compared bird abundance and species composition in 5 experimental riparian forest strips (20-m, 40-m, 60-m, and control [>300 m wide], intact strips, and 20-m-wide thinned strips), in boreal balsam fir (Abies balsamea) stands, for 3 years following clear-cutting. Bird densities increased 30-70% (P 0.05) thereafter to approximately pretreatment levels. The 20- and 40-m-wide riparian strips had highest mean bird densities, but also the fastest (P < 0.05) decreases thereafter. By the third year after clear-cutting, forest-dwelling species were less (P = 0.01) abundant than ubiquitous species in the 20-m strips. The golden-crowned kinglet (Regulus satrapa), Swainsons thrush (Catharus ustulatus), blackpoll warbler (Dendroica striata), and black-throated green warbler (D. virens) became nearly absent in 20-m strips. The removal of 33% of the trees in some 20-m strips resulted in a <20% decline of bird densities, a moderate effect that combined with the greater effect of strip narrowness. There was evidence that 60-m-wide strips are required for forest-dwelling birds. Bird populations may continue to decline in strips before regeneration of adjacent clear-cuts provides suitable habitat for forest-dwelling species

Food choice by white-tailed deer in relation to protein and energy content of the diet: a field experiment

Abstract Optimality models of food selection by herbivores assume that individuals are capable of assessing forage value, either directly through the currency used in the model or indirectly through other variables correlated with the currency. Although energy and protein are the two currencies most often used, controversy exists regarding their respective influence on food choice. Part of the debate is due to the difficulty of teasing apart these two nutrients, which are closely correlated in most natural forages. Here we offer a test of the assumption that energy and protein contents of the forage are both currencies that large mammalian herbivores can use when selecting their food. We observed feeding behavior of 47 wild white-tailed deer (Odocoileusvirginianus) during winter while individuals were presented with four experimental foods representing two levels of energy and protein (dry matter digestibility: 40–50%; crude protein: 12–16%). Using experimental foods allowed us to separate the influences of energy and protein and clearly distinguish between the roles of these two nutrients. Deer discriminated between foods through partial selection, and selected diets higher in energy but lower in protein. The observed choices appeared consistent with physiological needs of deer wintering at the study site, where digestible energy was in short supply in the natural environment while protein was probably not. Results are in good agreement with recent findings on domesticated ruminants. They support a basic assumption of optimality models of food selection that use energy and/or protein as a currency, although the physiological mechanisms behind the food selection process remain unclear. We urge students of food selection by herbivores to replicate our experiment with other foods and/or in other circumstances before more general conclusions are drawn.

Behavioural responses of moose to thermal conditions in the boreal forest

Abstract: Among ungulate species living in boreal regions, moose (Alces alces) are most likely to suffer from heat stress since they have a relatively low upper critical temperature (14 °C in summer and -5 °C in winter). We tested the hypothesis that moose adopt behaviours to reduce thermoregulatory costs. We predicted that moose exposed to high intensities of solar radiation or high air temperatures would 1) seek a type of vegetation association that provides thermal shelter and 2) reduce activity. We also predicted that these behaviours would be most evident in summer. Thermal-shelter use and activity of 30 free-ranging moose were measured over 3 y in a 940-km2 study area of boreal forest using GPS telemetry collars. The effect of solar radiation and air temperature on thermal-shelter use and activity were assessed using logistic and multiple regression analyses. Habitat use and activity rates of moose were related to air temperature but not solar radiation. The probability of finding moose in thermal shelters increased with air temperature in summer and fall. Moose activity did not decrease as air temperature increased, but it increased at night during hot periods. As expected, moose response to thermal conditions was most noted in summer. Our results suggest that moose reduce exposure to thermal stress by using thermal shelters during the day and by increasing nocturnal activity. These behavioural adaptations allow moose to cope with thermal stress on a small temporal scale. Negative effects of heat stress could be important in areas where air temperatures are very high for extended periods of time or where thermal cover is scarce.

FORESTRY PRACTICES AND THE RISK OF BIRD NEST PREDATION IN A BOREAL CONIFEROUS FOREST

Reconciling tree harvesting with the maintenance of forest bird populations is a major concern of integrated management. Because bird nest predation causes >50% of the nest losses in passerines and is known to vary according to habitat characteristics, we explored some aspects of avian nest predation in relation to forestry practices in a boreal coniferous landscape managed primarily for timber production in Quebec. Using artificial tree and ground nests with Common Quail (Coturnix coturnix) and plasticine eggs, we compared the risk of nest predation (1) in experimental riparian forest strips of different widths (20-m, 40-m, and 60-m unthinned strips; >300-m control strips; and 20-m thinned strips) and (2) in clearcuts experimentally subjected to different regeneration practices (plantations with chemical and mechanical weeding, and naturally regenerated clearcuts) between 1992 and 1995. The risk of ground nest predation was lower in naturally regenerated clearcuts (5% daily probability of predation) than...

Feedback effects of chronic browsing on life-history traits of a large herbivore.

1. Increasing ungulate populations are affecting vegetation negatively in many areas, but few studies have assessed the long-term effects of overbrowsing on individual life-history traits of ungulates. 2. Using an insular population of white-tailed deer (Odocoileus virginianus Zimmermann; Anticosti, Québec, Canada) introduced in 1896, and whose density has remained high since the first evidence of severe browsing in the 1930s, we investigated potential feedbacks of long-term and heavy browsing on deer life-history traits. 3. We assessed whether chronic browsing contributed to a decline of the quality of deer diet in early autumn during the last 25 years, and evaluated the impacts of reduced diet quality on deer body condition and reproduction. 4. Rumen nitrogen content declined 22% between two time periods, 1977-79 and 2002-04, indicating a reduction in diet quality. 5. After accounting for the effects of year within the time period, age and date of harvest in autumn, peak body mass of both sexes declined between the two time periods. At the end of November, males were on average 12% heavier and adult does 6% heavier in 1977-79 than in 2002-04. Hind foot length did not vary between time periods. 6. The probability of conception increased 15% between the two time periods, but litter size at ovulation declined 7%, resulting in a similar total number of ovulations in 2002-04 and in 1977-79. 7. Our results suggest that following a decline in diet quality, white-tailed deer females modified their life-history strategies to maintain reproduction at the expense of growth. 8. Deer appear to tolerate drastic reductions in diet quality by modifying their life history traits, such as body mass and reproduction, before a reduction in density is observed. Such modifications may contribute to maintain high population density of large herbivores following population irruption.

Reproductive Biology of Female Black Bears in Relation to Body Mass in Early Winter

We examined the influence of body mass in early winter on litter size, growth and sex ratio of young, as well as the influence of gestation and lactation on overwinter loss of mass among female black bears ( Ursus americanus ) in La Mauricie National Park, Quebec, Canada. All adult females weighing ≥77 kg gave birth and no female reproduced when weighing <56 kg. Litter size (two to four young) was influenced by maternal condition in early winter, and overwinter loss of mass greater for females producing litters of three and four young. For a particular litter size, heavier females tended to produce more male young than expected from an equal sex ratio. Maternal condition, however, could not explain the strongly male-biased sex ratio (2.5 males: 1.0 female) at birth observed in this population. Significance of sex ratio at birth in relation to the regulation of the population of bears at La Mauricie National Park is discussed.

VARIATION IN CALF BODY MASS IN MIGRATORY CARIBOU : THE ROLE OF HABITAT, CLIMATE, AND MOVEMENTS

Abstract Individual differences in body mass exert a major influence on several life-history traits of mammals. We investigated the factors influencing variation in body mass of calves of migratory caribou (Rangifer tarandus) at birth (June, 19 years of data) and in autumn (October, 15 years of data) in the Rivière-aux-Feuilles (Feuilles, 1991–2003) herd and the Rivière-George (George, 1978–2003) herd in Québec and Labrador, Canada. Mass at birth (hereafter, birth mass) did not differ between herds, possibly because part of their winter ranges overlapped. However, Feuilles calves were smaller in autumn than George calves, possibly reflecting differences in summer ranges. The birth mass of calves also varied with year, likely as the outcome of both intrinsic and extrinsic factors. Birth and autumn body mass were influenced positively by habitat quality in June, estimated by the normalized difference vegetation index. The North Atlantic Oscillation of the previous winter was positively correlated with autumn mass of the George calves. Previous winter snowfall was negatively related to the mass of George calves, and daily movement rates in summer were negatively correlated with the mass of calves of both herds in autumn. Birth mass was positively related with productivity in October in the George herd and also with productivity 3 and 4 years later, which corresponds to the beginning of reproduction of females. We suggest that a mechanism of delayed quality effect of the calves could have been involved in the decrease of fall productivity and population size of the George herd.

Daily activity patterns of female black bears in a northern mixed-forest environment

Activity patterns of 15 female black bears ( Ursus americanus ) were studied using motion-sensitive radiotransmitters during late summer and autumn of 1990 and 1991 in La Mauricie National Park, Quebec. Female black bears primarily were diurnal during this period, and no difference in activity patterns was detected between solitary females and females with young. Onset of activity followed sunrise by an average of 30 min, and cessation occurred on average 141 min after sunset. Activity and resting periods averaged 245 and 57 min, respectively. The proportion of active bears was highest during the ripening time of berries ( Rubus idaeus , Vaccinium myrtilloides , and Prunus virginiand ) in late August and of beechnuts ( Fagus grandifolid ) in early October. Bears denned earlier in 1991 than in 1990, probably because of the poor beechnut crop.

Evidence for a trade-off between growth and body reserves in northern white-tailed deer

We contrasted patterns of growth and accumulation of body reserves in autumn between two high-density (HD) white-tailed deer populations facing winters of different severity and length. Both populations occurred in the absence of effective predators and suffered from some forage competition based on reduced body masses. A third population living at low density (LD) and confronting long and severe winters (SW) served to distinguish the influence of food competition and winter severity on growth and body reserves. We estimated body components (water, protein, fat and ash) of deer during the first half of November and compared growth patterns between sexes and regions. HD-SW males continuted growth to an older age than HD males facing short and mild winters (MW) but females of both regions reached adult body mass at the same age. LD-SW deer exhibited a growth pattern similar to that of HD-SW animals but were the heaviest and the largest, suggesting that growth patterns are related to winter harshness (or length of the growing season) and that final body size is related to forage competition in summer. Sexual dimorphism became evident at an older age in the HD-SW population than in the HD-MW population, demonstrating that winter harshness does not affect immature males and females in the same manner. Fawns from the HD-SW population had proportionally longer legs and a higher percentage of body fat. Adaptations of immature deer to long and severe winters suggest that survival during the first winter represents the most critical step in the life span of northern white-tailed deer.

The low performance of forest versus rural coyotes in northeastern North America: Inequality between presence and availability of prey

Abstract Coyotes, which originate from central and southwestern North America, recently extended their range into forests of the Northeast. Forest coyotes occur in lower densities, have lower body reserves, and consume more fruits during summer than their counterparts occupying adjacent rural landscapes. We hypothesised that the forest landscape offered less animal prey to coyotes during summer than did the rural landscape. Coyote densities were higher in the rural landscape (2.7 animals 10 km-2) than in the forest landscape (0.5 animals 10 km-2) during the summer of 1997. During the summers of 1996 and 1997, coyotes in both landscapes fed mainly on wildberries (< 45% of dry matter intake), small mammals (< 10%), and snowshoe hare (< 10%). The biomass of the most abundant animal prey, snowshoe hares, was greater in the forest landscape (1.24 and 1.53 kg ha-1 in 1996 and 1997, respectively) than in the rural landscape (0.46 and 0.40 kg ha-1 in corresponding years). The biomass of the other major animal prey (small mammals), was comparable in both landscapes but irrupted during the second summer (0.09 and 0.50 kg ha-1 in 1996 and 1997, respectively). The biomass of fruits remained relatively constant in the rural landscape during the summers of 1996 and 1997 (ª 6 kg ha-1), but it tripled in the forest landscape during the second year (1.69 kg ha-1 in 1996 versus 5.30 kg ha-1 in 1997). Contrary to our prediction, the availability of animal prey in the forest landscape exceeded that in the rural landscape. Our results illustrate that the presence of prey does not correspond to its availability to predators. Coyotes appear poorly adapted for hunting in dense forest vegetation during summer and compensate for shortage of animal prey by consuming more berries.