Le dernier caribou du Nouveau-
Brunswick?

Vers la fin des années 1800, les populations de caribou avaient diminué dans le nord-est de l'Amérique du Nord.

Stephen Clayden, 
du Musée du Nouveau-
Brunswick, affirme : "L'extinction éventuelle du caribou au Nouveau-
Brunswick, en Nouvelle-Écosse
et dans les terres environnantes semble avoir coïncidé avec l'arrivée et la croissance rapide
de la population du cerf de Virginie." 

Cet article aborde différents aspects intéressants, y compris comment les efforts pour réintroduire le caribou en Nouvelle-Écosse et dans le Maine ont été un échec, et 
qu'il est fort probable que le caribou ne revienne jamais dans cette région.

The Last
New Brunswick Caribou?

Stephen Clayden
NB Museum
December 2000

hat caused the demise of the caribou in New Brunswick and elsewhere across the southern reaches of its historic range in North America? Several factors have been implicated. These vary in importance from region to region, but all involve human activity or its indirect consequences: overhunting, alteration, fragmentation, or elimination of habitats through logging, fire (or fire prevention), settlement, agricultural development and road construction, increased predation of young animals by bears or other large carnivores, and disease.

============= "Caribou Migrating" Engraving by  C. C. Ward,  published in in  Scribner’s Monthly, 1878, vol. 17, p. 237. The illustration is probably based on Ward’s observations of caribou in the barrens of Charlotte County, New Brunswick. =============

Although caribou numbers in northeastern North America were already much reduced by the late 1800s from those of previous centuries, the ultimate extinction of the species in New Brunswick, Nova Scotia, and adjoining mainland regions appears to have coincided with the influx and explosive population growth of white-tailed deer. Deer were rare in the Maritimes in the early 1600s, and remained so for most of the next three hundred years. A scarcity of immature forest cover and clearings, their principal habitat, was probably the main factor limiting expansion of the white-tail’s range. But as deer spread northward in the wake of European settlement, both caribou and moose populations were affected. In areas with a high density of deer, many moose succumbed to a mysterious sickness. However, while moose and deer established a somewhat precarious coexistence, caribou perished.

A telling glimpse of the reversal in fortunes of caribou and deer in New Brunswick is contained in a reminiscence by guide and outfitter Bert Moore (1883-1972), published in the Winter 1996-1997 issue of the magazine New Brunswick Tree and Forest: "In 1900," wrote Moore, "there were very few deer in the Tobique–Nepisiguit country, but caribou were there in great numbers." He attributed the precipitous subsequent decline of the caribou to a rapid increase in the deer population. This, he assumed, led to competitition between the two species for a limited food supply, and to the caribou, now supposedly under-nourished and weakened, becoming more susceptible to disease.

============================ "Woodland Caribou Hoofs" Engraving by C. C. Ward, published in Scribner’s Monthly, 1878, vol. 17, p. 236. Ward writes: "The construction of the caribou’s hoof ... differs from that of any other animal of the deer tribe, and is wonderfully adapted to the services it is required to perform, and enables the animal to travel in deep snows, over frozen lakes and icy crusts, when the moose and deer are confined to their yards, and at the mercy of their foes. ... Both sexes use their hoofs to clear away the snow in searching for mosses [lichens] on the barrens ... The hoof figured ... is drawn from nature, and measures fourteen inches in circumference, five inches in diameter, and has a lateral spread [when expanded] of ten inches." ============================

Moore’s description of this disease is most intriguing. He characterizes the animals as suffering from tuberculosis, and notes that several were found dead in the woods. The last caribou he saw, in November 1928, was "walking in circles. I caught and examined it without difficulty," he notes, "and the next morning it was lying dead almost in the camp yard. One buck deer and two small bull moose were found in the Nictau Lake region about that time in a similar condition, and all were found dead later."

What is particularly interesting about Moore's account is that it may be the earliest on record of the symptoms in caribou of a parasite spread by its main host, the white-tailed deer. It was not until the early 1960s that this parasite, a tiny roundworm with the formidable name Parelaphostrongylus tenuis, was first shown to be the cause of "moose sickness." Further studies soon determined that its effects on caribou were similar to those in moose, but more severe and quick to develop. The most obvious outward signs of the disease are weakness or paralysis of the hind quarters, a loss of fear of humans, and a general loss of motor coordination, resulting in shaking, staggering or walking in circles before the animals’ eventual death—just as noted by Moore. In deer, the infection is non-lethal and normally without debilitating effects.

Parelaphostrongylus is passed from deer to caribou (or moose) via an intermediate host: any of various species of slugs or snails. The latter are ingested inadvertently by the grazing caribou. The worms then invade the central nervous system, moving to the meninges surrounding the spinal cord and brain—thus the common name, "meningeal worm." In deer, the mature worms produce eggs, and the resulting larvae are carried in the bloodstream to the lungs. From here they pass via the airways into the mouth, where they are swallowed and eventually expelled (still alive) in the feces, only to penetrate the feet of passing slugs or snails and complete the cycle. Deer with lungs heavily infected by the parasite may be predisposed to secondary infection by bacteria, and this could account for the "tuberculosis" (more likely pneumonia) in a buck deer observed by Bert Moore.

At least four separate efforts to reintroduce caribou to Nova Scotia and Maine have failed—all apparently for the same reason. Fifty-one animals were released in Cape Breton Highlands National Park in 1968 and 1969, but none was sighted after 1972, and a study concluded that the herd probably fell victim to disease after contraction of the meningeal worm. The only surviving population of caribou south of the St. Lawrence River inhabits the high plateau of the Chic-Choc Mountains in Gaspésie Park in Quebec. Although these animals descend to lower elevations in winter, and possibly encounter deer, there is little chance of them picking up the meningeal worm at this time of year. A more significant threat may now be the recently arrived coyote. A coyote-control program was carried out in Gaspésie Park in the early 1990s.