Increases in body weight and nutritional status of transplanted Alaskan caribou

Body weight and natality rate in ungulates can be useful indices to nutririon, bur they may also be influenced by genetic and climatic factors. Because caribou {Rangifer tarandus granti) are distnbuted as discrete populations ot metapopulations (i.e., herds) that are usually reproductively isolated from each other for unknown periods, it is difficult to separate the influence of genetics and nutri t ion on body weight, especially where historical data are lacking. To help elucidate the influence of nutrit ion on potential variation in body weight and natality of caribou in Alaska, we reviewed data for body weight and natality in 5 populations which resulted from Transplants to previously ungrazed ranges, or to areas where reindeer and caribou had been absent for many decades. In 2 of 5 populations body weight increased significantly, and l ikely increased in the other 3 populations, but data were insufficient. Natal i ty rate increased in all 5 populations, proportion of fecund yearlings was high and 3 of the 5 newly established herds increased ar about the maximum biological potential for the species (X=1.35). In the A d a k transplant, a lactating yearling was documented. These 5 transplanted populations provide additional evidence that body weight and natality rate in Alaskan caribou are sensitive to changes in population density and relatively short-term (i.e., 10 years) increases in grazing pressure independenr of climate and genetics. K e y w o r d s : natal i ty , Rangifer tarandus grand. Rangifer, Specia l Issue N o . 12, 1 3 3 1 3 8

Experimental transplants can sometimes provide such control and help biologists assess the influence of grazing history and population density on herd nutrition (Klein, 1968).In this paper we review 5 Rangifer, Special Issue No. 12, 2000 Alaskan caribou transplants and recent data on changes in body weight and natality in transplanted and parent herds, and make inferences about the importance of population density, previous grazing pressure, and climate on body weight and natality in Alaskan caribou.We consider the term "herd" to be synonymous with population or metapopulation because opportunities for interbreeding occur, but are uncommon, and dispersal seems to occur at very low levels (Valkenburg et al. 1996;Valkenburg, 1997).

Adak Island transplant
In response to a request from the military, caribou were transplanted from the Nelchina herd (Fig. 1) to previously ungrazed Adak Island in 1958 and 1959 (Jones, 1966;Burns & McKnight, 1973).
Caribou were captured as 1-or 2-day-old calves and held in captivity for 5 to 8 weeks before being released.Following release, calves from both transplants were bottle fed until 6 August and then left to fend for themselves.The Adak transplant was unique because caribou were removed from the parent herd as newborn calves, and thus had no opportunity to acquire parasitic oestrid larvae (Hypoderma tarandi and Cephenemyia trompe).
Data on body weight and nutrition of transplanted caribou are scant, but it appears that body weight and natality increased (Table 1).On Adak, mean weight of 5 "adult" bulls taken in August 1964-1968 was probably higher than in the parent Nelchina herd, but Skoog (1968) presented no estimate of variance, and a statistical test was not possible (Table 1).However, most (compared with 13% in the parent herd) yearling females were pregnant on Adak, and a lactating yearling (indicating the animal conceived as a calf) was killed in autumn 1966 (Glenn, 1967).In addition to increased production in young females, the Adak herd also exhibited maximal population growth (Table 1).

Kenai Peninsula transplants
The first Kenai Peninsula transplants took place in However, the Kenai Lowlands herd increased slowly, apparently because of predation (Spraker, 1992).
The herd then fluctuated in size with lows of about 200 and 300 in 1978 and 1988, respectively, and highs of 450 in 1986 and 500 in 1996.In April 1996, when the herd was at its peak of about 500, the mean weight of a sample of 11 female calves was similar to the heaviest cohorts of calves from the parent Nelchina herd during 1992-1997 (Table 1).
In  (Valkenburg, 1997) (Table 1).These calves were significantly heavier (P<0.001,£=4.84) than calves weighed during the same period in the Kenai Mountains herd, despite similarities in elevation, growing season length, and physiographic characteristics of their ranges (Table 1).

Nushagak Peninsula transplant
In 1988, caribou were transplanted from the Northern Alaska Peninsula herd to a vacant range on the Nushagak Peninsula about 100 km to the west (Fig. 1).The transplanted caribou increased rapidly (Table 1), and all females aged 2 years or older were fecund during 1988-1993 (Hinkes & Van Daele, 1996).At the time of the transplant, the  1) (Valkenburg, 1997).
In 1997, when population density had increased to 0.8/km 2 in the transplanted Nushagak herd, body weight of calves was not greater than in the Northern Alaska Peninsula herd (P=0.28,£=1.11) (Table 1).

Discussion
The 5 transplanted herds reviewed here provide additional evidence that body weight and natality in many established Alaskan herds are significantly limited by density-dependent nutritional factors that are independent of climate and genetics.On Adak, the longer growing season, lack of parasitic insects, and potential availability of green forage in winter could have accounted for increased body weight and productivity compared with parent stock in the Nelchina herd (Jones, 1966;Thomas & Kiliaan, 1990).On the Nushagak Peninsula, however, body weight of calves was greater in the transplanted herd from 1992 to 1995 despite the similar summer climate and physiography (Hinkes & Van Daele, 1996) (Table 1). 136 The Kenai transplants also demonstrate the potential for increased body weight and fecundity on pristine ranges.Calves from the 1996 cohort in the Killey River herd were significantly larger than any of the Nelchina cohorts.

In the Kenai
Mountains herd initially, and in Killey River herd natality in 2-year olds must have been much higher than that reported for the Nelchina, because the Kenai Mountains herd grew at nearly the biological maximum (indicating virtually all yearlings were pregnant), but the highest reported pregnancy rate in Nelchina yearlings was only 13% (Skoog 1968;Bergerud 1980: 568).
Although changes in body weight and natality rate were not obviously related to crude summer density across herds (Table 1), declines in body weight and natality occurred after relatively short periods of grazing pressure as density within herds increased.Decreasing summer nutrition is the factor most likely to cause observed declines in natality and body weight (Skogland, 1984;1985;Eloranta & Nieminen, 1986;Reimers, 1997).Reduced body weight and natality began to occur in the Kenai Mountains herd after only 10 years of grazing, and summer density increased only to about 0.3/km 2 before herd growth slowed.In 1995 crude density was still only about 0.5/km 2 when body weight of female calves was similar to the parent Nelchina herd where summer density was 4.7/km 2 (Table 1).
Inherent physiogeographic and climatic factors, rate of population growth, and opportunity for dispersal undoubtedly determine the summer density that herds can achieve.For example, on St. Matthew Island very high summer densities were achieved (18/km 2 ) because of the high quality and quantity of summer forage, the long growing season, lack of opportunity for dispersal, and high population growth rates due to the virtual absence of predators (Klein, 1968).
On mainland ranges where large predators are present, predation can have a profound dampening effect on population growth rate and density when functional and numerical responses occur and prey vulnerability increases as nutrition declines (Dale et al, 1994;Valkenburg et al, 1996).Population growth was apparently restrained immediately after
1965 and 1966, and the caribou were again taken from the Nelchina herd.Release sites on the Kenai Peninsula had received no grazing by reindeer or caribou since about 1900 Fig. 1).Although there are no data on body weight or relative nutritional status in the years immediately following the transplant, a bull immobilized and measured in the early 1980s from the Kenai Lowlands herd had antlers unofficially scoring 476 2/8 Boone and Crockett points, more than any other caribou in the Boone and Crockett records(Boone & Crockett Club, 1993).The shed antlers of this animal were retrieved and mounted and are on display at the Anchorage Department of Fish and Game office.
1985 and 1986 caribou were again relocated to the Kenai Peninsula from the Nelchina herd.At that time, the Nelchina herd was growing, from a herd size of about 27 000, and approaching a moderate density of about 0.5 caribou/km 2 (Van Ballenberghe, 1985).The 2 transplants resulted in formation of 3 additional herds, the largest of which became known as the Killey River herd (Fig. 1).This herd increased from about 70 caribou in summer 1987 to about 350 in 1997 (A,= 1.18).In 1996ft a u o Rangifer, Special Issue No. 12, 2000 the mean weight of a sample of 10-month-old female calves exceeded previously recorded calf weights for all Alaskan herds introduction due to predation by wolves (Canis lupus), coyotes (C.latrans) and dogs (C.familiaris) in the Kenai Lowlands herd (Spraker, 1995).However, in the Kenai Mountains herd and the Killey River herd, although both wolves and grizzly bears (Ursus arctos) were present and lightly hunted, near maxi-RangiSer, Special Issue No. 12, 2000 mum caribou population growth continued for 10 years after introduction.This could either be due to a lag in predator hunting behavior, the low vulnerability of caribou on a very high plane of nutrition, or both.In the Nushagak herd large predators are scarce and particularly vulnerable to hunting.