Comparative body composition strategies of breeding and nonbreeding female caribou

Abstract

We evaluated the effects of season and reproductive status on body fat and body protein masses of freeranging female barren-ground caribou (Rangifer tarandus granti). Body fat mass fluctuated markedly during the year (by a factor of at least 2) in both reproductive classes, but whereas maximum fatness occurred in autumn (September-November) in nonbreeding females, it did not occur until late winter (March-April) in breeding females. Seasonal changes in dry body protein mass were relatively modest, with annual maxima averaging only 31-43% higher than annual minima. Moreover, seasonal differences between the reproductive classes were not significant except in November-December. Absolute fat deposition by both breeding and nonbreeding females was highest in summer, though fat deposition increased relative to protein deposition in autumn. Between June and September, the primary deposition of body protein in breeding females contrasted with the primary deposition of body fat in nonbreeding females. As a result, breeding females were highly compromised in their fat deposition but not in their protein deposition, which approximated levels in nonlactating females. Differences in body composition between breeding and nonbreeding females were highest in autumn and lowest in early spring because of divergence in summer and convergence in winter.Résumé : Nous avons évalué les effets de la saison et du statut reproducteur sur la masse des graisses et des protéines de femelles du Caribou de Grant (Rangifer tarandus granti). La masse des graisses a fluctué fortement au cours de l'année (au moins par un facteur de 2) chez les deux classes de femelles, mais alors que la masse des graisses est devenu maximale à l'automne (septembre-novembre) chez les femelles non reproductrices, elle n'a pas atteint son maximum avant la fin de l'hiver (mars-avril) chez les femelles reproductrices. Les changements saisonniers de la masse sèche des proteines étaient relativement peu importants puisque les maximums annuels n'ont été que de 31 à 43% plus élevés que les minimums annuels. De plus, les différences saisonnières entre les deux classes de femelles n'étaient pas significatives sauf en novembre-décembre. L'accumulation des graisses (en valeur absolue) se faisait surtout en été chez les femelles des deux groupes, même si à l'automne elle devenait plus importante que l'accumulation de protéines. Entre juin et septembre, nous avons constaté une accumulation importante de protéines chez les femelles reproductrices, alors qu'au même moment, chez les femelles non reproductrices, il se faisait une importante accumulation de graisses. Conséquemment, les femelles reproductrices se sont trouvées très compromises dans leur accumulation de graisses, mais non dans leur accumulation de protéines dont les concentrations se rapprochaient de celles des femelles non nourricières. Les différences dans la composition corporelle entre les femelles reproductrices et les femelles non reproductrices se sont avérées maximales à l'automne et minimales au début du prin...

Using ultrasound measurements of rump fat to assess nutritional condition of woodland caribou in northern British Columbia, Canada

“…Pregnant females are likely most sensitive to these types of restrictions during the third trimester when physiological demands of fetal growth are the highest. Monitoring changes in body protein, however, is challenging because of the relatively small changes that occur throughout the year (approx 9.5-11.2% of body mass for breeding female caribou, Chan McLeod et al, 1999). Recent use of nitrogen isotopes in snow urine to assess nitrogen balance in late winter (Parker et al, 2005;Barboza & Parker, 2006) is promising, but this technique requires validation in wild populations of caribou.…”

“…Recognizing that the deposition and mobilization of fat varies with age (Dauphiné, 1976;, previous demands of reproduction (ChanMcLeod et al, 1994), and across the winter season (Thomas & Kiliaan, 1998;Chan-McLeod et al, 1999), ultrasonography can be used as a non-invasive technique in the field to assist in evaluating nutritional condition of caribou. Similar to data collected from carcass evaluations in previous studies on barrenground caribou (e.g., Dauphiné, 1976;Thomas & Kiliaan, 1998), the non-pregnant woodland caribou in our sample had less rump fat than pregnant individuals.…”

“…Quantifying body fat and protein is an important component of defining the nutritional condition of individuals within populations (Gerhart et al, 1996a), and has typically involved harvesting individuals (e.g., Anderson et al, 1972;Heard et al, 1997;Ouellet et al, 1997;Chan-McLeod et al, 1999). Harvesting animals may be appropriate for highly reproductive and/or large populations of cervids [e.g., barren-ground caribou (R. t. groenlandicus)], but is not applicable for cervid populations that occur at low densities, are endangered, and/or have low rates of recruitment [e.g., woodland caribou (R. t. caribou)].…”

Modeling energy and protein reserves in support of gestation and lactation: glucose as a limiting metabolite in caribou and reindeer

“…Fat reserves vary independent of protein among populations and are dependent on reproductive history of the female (Parker et al, 2005(Parker et al, , 2009. Although body protein is often thought to be only poorly mobilized, data from Rangifer populations would challenge this assumption since the seasonal change in body protein is about 26-42% (Huot 1989;Gerhart et al, 1996;Chan-McLeod et al, 1999) giving a LPR of 3-6 kg. e 4.6 kg protein loss (Fig.…”

Morphology of Female Woodland Caribou, <em>Rangifer tarandus caribou</em>, in Saskatchewan

“…In particular, Skogland (1983) argued that morphology was density-dependent and related to the factors limiting population growth. Both Skogland (1983) and Chan-McLeod et al (1999) reported that female R. tarandus that had reproduced successfully were significantly lighter the following winter than those that had not. Here, I present the first description of Woodland Caribou from central Saskatchewan and a discussion of their morphology relative to limiting factors.…”