The influence of top-down, bottom-up and abiotic factors on the moose (Alces alces) population of Isle Royale

Long-term, concurrent measurement of population dynamics and associated top-down and bottom-up processes are rare for unmanipulated, terrestrial systems. Here, we analyse populations of moose, their predators (wolves, Canis lupus), their primary winter forage (balsam fir, Abies balsamea) and several climatic variables that were monitored for 40 consecutive years in Isle Royale National Park (544 km2), Lake Superior, USA. We judged the relative importance of top-down, bottom-up and abiotic factors on moose population growth rate by constructing multiple linear regression models, and calculating the proportion of interannual variation in moose population growth rate explained by each factor. Our analysis indicates that more variation in population growth rate is explained by bottom-up than top-down processes, and abiotic factors explain more variation than do bottom-up processes. Surprisingly, winter precipitation did not explain any significant variation in population growth rate. Like that detected for two Norwegian ungulate populations, the relationship between population growth rate and the North Atlantic Oscillation was nonlinear. Although this analysis provides significant insight, much remains unknown: of the models examined, the most parsimonious explain little more than half the variation in moose population growth rate.     

Dermacentor albipictus on moose (Alces alces) in Ontario.

Fifty-five moose (Alces alces) collected from 1963 to 1965 in the Chapleau Crown Game Preserve of northern Ontario were examined for ectoparasites. Dermacentor albipictus was the only parasite recovered. D. albipictus was absent from 15 moose examined during June, July and August; first observed on 1 or 2 moose examined in September; and present on all 38 moose collected from October to May. Ticks were not evenly distributed on the body. Infestations varied from 32 to 13,490 ticks/moose for 14 individuals. Levels of infestation observed did not have an obvious adverse effect on the health of the moose.     

Increased osteoarthritis in moose from Isle Royale

Over the past 30 yr, moose (Alces alces) in Isle Royale National Park (Michigan, USA) exhibited a several-fold increase in the prevalence of osteoarthritis, or degenerative joint disease (DJD). Available evidence points to an environmental explanation for this change. Greater physical activity among afflicted moose is not a likely contributing factor, nor is genetic change in the population. The possible introduction of an unspecified disease agent cannot be dismissed at this time. Moose exhibiting the highest prevalence of DJD were those born during a period of severe undernutrition, and it is hypothesized that nutritional stress early in life was responsible for increased joint disease during senescence. Such an etiology for osteoarthritis has not been suggested previously for any species.     

Elaeophora schneideri in moose (Alces alces) from Colorado.

Two adult moose (Alces alces) from Colorado (USA) were naturally infected with Elaeophora schneideri. Both animals had patent infections indicating that moose may serve as definitive hosts. Gross and histological lesions were characterized by fibromuscular intimal proliferation within the carotid arteries and rete mirabile cerebri. This is the first report of Elaeophora schneideri in moose from Colorado.     

Low-dose meningeal worm (Parelaphostrongylus tenuis) infections in moose (Alces alces)

Parelaphostrongylosis has a rapid onset and is lethal in neonatal moose (Alces alces) when large numbers of third-stage Parelaphostrongylus tenuis larvae (L3) are given experimentally. Little is known, however, about the severity and prognosis of infections acquired naturally by accidentally ingesting terrestrial gastropods which are rarely infected and have few larvae. To investigate the relationship between infecting dose, age of moose, and severity of disease, five calves were given low doses of three to 10 L3 when five (n = 2) or 9.5 mo old (n = 3). Each of two animals initially given low doses were later challenged with a dose of 15 L3. As positive controls, two calves were given doses of 15 and 30 L3, considered to be high. All five calves given low doses showed abnormal locomotory signs at 20-28 days postinoculation (DPI) that progressively became more pronounced with hind quarter weakness and front lameness. However, after 77-130 DPI, signs diminished markedly in two of these animals and disappeared in another two. Challenge infections of 15 L3 given 199 days after initial infections had no noticeable effects although an immature worm, probably resulting from the challenge, was found in the spinal cord of one animal killed 51 days later. Two positive control animals given the high doses of 15 and 30 L3 showed moderate to severe, non-resolving, locomotory signs and had to be euthanized. Results demonstrate that single, low doses of three to 10 P. tenuis L3 cause moderate disease in moose calves but over time, some worms die and animals can recover. A degree of protection may develop against future infection.     

Geographical variation of antler morphology of moose (Alces alces) in Russia

We attempt to identify geographical subdivisions within the range of moose according to antler size for a more correct trophy evaluation in the СIC system (The International Council for Game and Wildlife Conservation). Traditionally, this division coincides with subspecific division of trophy animal species. That is why we partially touch upon the problem of the geography of moose subspecies in Eurasia. Catalogs of hunters’ trophies that were available to us served as the research material (1,047 trophies in total). We were choosing the same measurements for moose antlers evaluated by different methods. They are overall spread, circumference of beam, width of palm, and number of tines. We applied multivariate statistic methods to the findings, enlarging the geographical division groups step by step. As a result, we suggest four geographical groups: European, Siberian, the north of the Far East, and the south of the Far East. In principle, this division corresponds to the subspecies: European (Alces alces alces L., 1758), east Siberian (A. a. pfizenmayeri Zukowsky, 1910), Chukotka or Kolyma (A. a. buturlini Chernyavski et. Zhelesnov, 1982), and Ussuri (А. а. cameloides Milne-Edwards, 1867). We consider it incorrect to draw the line between the European and Siberian groups along the river Yenisei. It is more correct to move it to the Urals.     

Tick (Dermacentor albipictus)-induced winter hair-loss in captive moose (Alces alces)

Five captive moose calves each infested with 42,000 larval Dermacentor albipictus, six calves each infested with 19,000-21,000, and five control moose were observed for changes in hair-loss, body condition and number, stages, and distribution of the tick. Winter hair-loss was observed only in moose infested with ticks and was correlated positively with the total number of adult ticks. Hair-loss associated with ticks was minimal from October to January, but rapidly increased from February to April when up to 44% of hair had been removed. The pattern of hair-loss was similar in all moose with the neck, shoulders, withers, and perianal areas losing the most hair. Moose with extensive premature hair-loss had less pericardial and abdominal visceral fat than moose with little or no hair-loss.     

Patterns of hunting mortality in Norwegian moose (Alces alces) populations

We used a simple life table approach to examine the age-specific patterns of harvest mortality in eight Norwegian moose populations during the last 15 years and tried to determine if the observed patterns were caused by hunter selectivity. The general opinion among local managers is that hunters prefer to shoot female moose not in company with calves to keep a high number of reproductive females in the population (and because of the emotional stress involved in leaving the calf/calves without a mother), and relatively large males because of the higher return with respect to meat and trophy. In support of the former view, we found the harvest mortality of adult females to be higher among pre-prime (1–3 years old) than prime-aged age classes (4–7 years old). This is probably because prime-aged females are more fecund and, therefore, more likely to be in company with one or two calves during the hunting season. As the season progressed, however, the selection pressure on barren females decreased, probably due to more productive females becoming ‘legal’ prey as their calf/calves were harvested. In males, we did not find any evidence of strong age-specific hunter selectivity, despite strong age-dependent variation in body mass and antler size. We suggest that this was due to the current strongly female-biased sex ratio in most Norwegian moose populations, which leaves the hunters with few opportunities to be selective within a relatively short and intensive hunting season. The management implications of these findings and to what extent the results are likely to affect the future evolution of life histories in Norwegian moose populations are discussed.Electronic Supplementary Material Supplementary material is available for this article at and accessible for authorised users.     

Mineral licks as a sodium source for Isle Royale moose

Summary Natural mineral licks and their use by moose (Alces alces) on Isle Royale National Park, Michigan, were studied during 1982–85. The distribution of known licks suggested that they occurred in association with glacial debris, primarily in the western portions of the island. Moose utilized mineral springs extensively during the spring-summer period, and at least 5 licks were used year-round. During summer, a pronounced diel pattern of moose visitation was apparent, with peak use occurring between 0400–0800 h. Although daytime lick use declined by late June, morning and evening use continued to be relatively high throughout the study period. Peak lick use coincided with leaf-emergence in spring. Moose continued to utilize mineral licks despite the availability of ponds containing aquatic plants. Sodium appeared to be the element attracting moose to licks where they ingest copious amounts of water. Observed sodium ingestion rates (0.35 g/min) at licks indicate that licks provide a more concentrated source of sodium compared to aquatic plants (0.023 g/min). Based on the data presented, we reject the conclusions of earlier workers that aquatic plants constitute the only significant source of sodium for Isle Royale moose.     

Geographical variation in body weight and sexual size-dimorphism of Norwegian moose (Alces alces)

Geographical variation in male carcass weight, and sexual dimorphism in size was studied in 19 populations of Norwegian moose ( Alces alces (L.)).
Significant age-specific variation in male carcass weight was found for all the populations studied up to the age of 4 1/2 years, but in some populations maximum weight was not reached until at least 5 1/2 years. Increase in the mean weight of females after the age of 2 1/2 years was not significant. Only a weak relationship existed between mean yearling and adult bull weights in a population. However, within both the southern (< 62°N) and northern (> 62°N) parts of the country, yearling carcass weight was a good predictor of adult bull weight in a region.
Adult bull weight in a region was best predicted from the increment in mean carcass weight observed between 1 1/2 and 3 1/2 years of age. Within a region, variation in age-specific carcass weight between cohorts of bulls from different years was also well predicted from annual variation in growth increment.
Those patterns reveal a sexual difference in strategy of body growth. The adult weight of females is probably strongly determined by the weight gained by the time of onset of reproduction. The males have available a longer period for growth in body weight. They are therefore able to compensate for low weights early in life by increased gain of weight in later years, that provide good conditions for growth.
Geographical variation in the degree of sexual dimorphism in size correlated only poorly with adult male size. We suggest that the sexual size-dimorphism is a result of reproductive constraints of the female, i.e. in populations living in poor conditions and having small body size, the onset of reproduction prevents further gain in body weight.     

Hematology and serum chemistry reference ranges of free-ranging moose (Alces alces) in Norway

Baseline reference ranges of serum chemistry and hematology data can be important indicators for the status of both individuals or populations of wild animals that are affected by emerging pathogens, toxicants, or other causes of disease. Frequently, reference ranges for these values are not available for wildlife species or subspecies. We present hematologic and serum chemistry reference ranges for moose (Alces alces) adults, yearlings, and calves in Norway sampled from 1992-2000. Additionally, we demonstrated that both induction time and chase time were correlated with initial rectal temperature, although they were not significantly correlated with cortisol, aspartate aminotransferase, glucose, or creatine kinase. Overall, the reference ranges given here are similar to those given for American moose, with a few differences that can be attributed to environment, testing methodology, or subspecies or species status. This is the first report, to our knowledge, of reference ranges for moose in Norway.     

Genetic diversity of moose (Alces alces L.) in Eurasia

Polymorphism of nucleotide sequence of D-loop fragment of the mitochondrial DNA was studied in 20 moose from several local populations on the territory of Eurasia. Three main haplotype variants of D-loop were detected by molecular phylogenetic method, which formed three clusters named European, Asian and American. Intraspecies variation in the length of HVSI of D-loop of the mitochondrial DNA of moose was revealed. In the Far Eastern and Yakutian moose, haplotypes with a 75-bp deletion were found, which were most similar with haplotypes (also with the deletion), earlier observed in North American moose [1]. The highest diversity of the haplotypes of mitochondrial DNA is characteristic of Yakutia and the Far East (where three haplotype variants were found), which demonstrates the probable role of the region as the center of the species or as the region of ancient population mixture. The geographic region might be considered as a probable source of ancient moose migrations from Asia to America, basing on the data of distribution of mitochondrial haplotypes of D-loop and alleles of MhcAlal-DRB1. Divergence of nucleotide sequences of haplotypes with the 75-bp deletion (forming the American cluster on the phylogenetic tree) was the lowest (0.4%), which evidences respectively recent origin of the group of haplotypes. In Europe, only haplotypes of mitochondrial DNA referred to European variant were observed. Basing on analysis of variation of nucleotide sequences of D-loop, exon 4 of kappa-Casein and exon 2 of MhcALal-DRB1, we demonstrated that Eurasian moose studied belong to the unique species, which has probably passed through a bottle neck. The time of the origin of modern diversity of D-loop haplotypes of the species was estimated as 0.075-0.15 Myr ago.     

Telemetered heart rate as an index of energy expenditure in moose (Alces alces)

Metabolic rate, heart rate and respiratory rate of three adult moose were monitored simultaneously on selected days between January 1982 and October 1983. Heart rate was successfully monitored using two types of implanted radio transmitters. Metabolic rate was significantly (P less than 0.001) correlated with heart rate for individual animals (r = 0.94-0.98). The relationship was best described by an exponential equation. A mean weighted equation predicted metabolic rate within 9% of individual equations. In adult moose cows, heart rate was a more reliable predictor of energy expenditure than respiratory rate.     

Parasites of moose (Alces alces) from an agricultural area of eastern Ontario

Viscera of 16 moose and hide samples of 24 moose (Alces alces) shot in eastern Ontario in 1985 were examined for parasites. Two species of trematodes, one species of cestode, five species of nematodes and one species of tick were recovered. One nematode species, Trichuris discolor, is reported for the first time from moose. Our results suggest that the parasite fauna of the moose may have been influenced by the absence or scarcity of other species of wild cervids or carnivores and by the presence of domestic livestock.     

Echinococcus granulosus (Cestoda: Taeniidae) infections in moose (Alces alces) from southwestern Quebec

Investigation of the distribution of larval Echinococcus granulosus in a moose population from southwestern Quebec revealed a distinct and stable pattern of infection with a prevalence of 44% (n = 580). Positive correlations between moose age and the intensity, mean cyst weight and biomass of the hydatid cysts suggested a process of continued parasite acquisition and cyst growth. The distribution of cyst sizes within individual moose provided circumstantial evidence of interaction between cysts, perhaps mediated through the host's immunological response.     

Detection of anti-parelaphostrongylus tenuis antibodies in experimentally infected and free-ranging moose (Alces alces)

Confirming Parelaphostrongylus tenuis infection in moose (Alces alces) and other susceptible hosts is difficult. An enzyme-linked immunosorbent assay (ELISA) was developed using the excretory-secretory (ES) products of third-stage P. tenuis larvae (ES-ELISA) and the test applied to serum samples obtained from seven moose calves (5-9.5 mo old) given infective larvae (L3) in doses approximating those likely to be received in nature (3-30 L3). Anti-P. tenuis immunoglobulin G antibodies were detected in all seven inoculated moose during the course of infection until the termination of experiment 61-243 days post-inoculation (DPI). Five animals tested between 16-25 DPI had significant antibody levels, while a sixth animal did not test positive until 46 DPI. The seventh animal was not tested until 199 DPI. Antibody levels remained elevated in all five animals that harbored adult worms at the termination of the experiment. Whereas, antibody levels showed a gradual decline in the two remaining animals, presumably because of death of worms, and antibodies were undetected in one animal at the time of necropsy. The other animal displayed an anamnestic increase in antibody level following a challenge inoculation of infective larvae. Terminal and peak optical density (OD) values detected by ES-ELISA strongly correlated with inoculation dose (r = 0.98, P = 0.02 and r = 0.95, P = 0.04, respectively) among animals harboring adult worms (n = 4) but not significantly with the number of worms recovered postmortem (peak OD, r = 0.82, P = 0.18; terminal OD, r = 0.93, P = 0.07). Unlike the ES products, use of somatic antigens of the adult worm in ELISA did not provide satisfactory results. Antibodies to P. tenuis were detectable by ES-ELISA in two of 21 free-ranging moose from an enzootic area but not from any of 23 animals from a non-enzootic area. The ES-ELISA appears to be a useful test for assessing exposure of moose to P. tenuis.     

Differences in urinary chemistry profiles of moose on Isle Royale during winter

During winters 1987-1988 (I) and 1988-1989 (II), we assessed the physiological status of moose (Alces alces) residing on the west and east ends of Isle Royale (Michigan, USA) by collecting and chemically analyzing urine deposited in snow (snow-urine) from January to early March. Samples were assayed for urea nitrogen (U), sodium (Na), potassium (K), calcium (Ca), phosphorus (P) and creatinine (C). Throughout both winters, elevated urinary U:C ratios in snow-urine samples collected from east-end moose compared to west-end moose indicated greater dietary energy deprivation and accelerated net catabolism of endogenous protein. Sodium: C ratios were low throughout the study and were similar between moose from both ends of the island, except during the middle of winter I. Greater K:C, P:C and Ca:C ratios in east-end moose compared to west-end moose throughout winter I, and increases in these ratios and U:C in east-end moose from middle to late winter during the second year provided additional evidence of a greater deterioration in condition in east-end moose. The superior nutrition provided to moose on the west end of the island was associated with more developed soils and diverse vegetation and a lower stem density of balsam fir compared to the east end.