Deer, moose and caribou

In the Bras d'or Lake Bio­sphere Re­serve

The Victoria Standard - - Environment - ANNAMARIE HATCHER

Septem­ber marks the be­gin­ning of the rut­ting sea­son for moose (in Mi’kmaq: tia’m) in the Bras d’or Lake Bio­sphere. This time is ex­cit­ing for the amorous moose and the hunters! The noisy an­tics of the ex­citable males may be one of the rea­sons that the Septem­ber moon is called Wikumkewiku’s, or mate­call­ing time, in Mi’kmaw cul­ture. An­other im­por­tant un­gu­late (hoofed an­i­mal) that may have played a part in the nam­ing of the Septem­ber moon was the rein­deer, or caribou (in Mi’kmaq: qalipu). Although we have none in Cape Bre­ton now, they played a sig­nif­i­cant role here in the past.

The caribou is one of the main char­ac­ters in a story that in­cludes the closely-re­lated moose and white-tailed deer. When Euro­peans first joined the Mi’kmaq in Cape Bre­ton (in Mi’kmaq: Unama’ki) moose were the largest mem­bers of the deer fam­ily here. Ac­cord­ing to in­for­ma­tion from Nova Sco­tia’s De­part­ment of Nat­u­ral Re­sources they suc­cess­fully co-ex­isted with one other un­gu­late, the main­land caribou, un­til the 1920s. The demise of caribou in Cape Bre­ton was then blamed on over-har­vest­ing and habi­tat loss. How­ever, the last caribou was seen at about the time that a new species, the white-tailed deer (in Mi’kmaq: lentuk), be­came es­tab­lished on the is­land. Tim­ing is every­thing, isn’t it?

A suc­cess­ful re­lease of white-tailed deer in the Digby and Hal­i­fax ar­eas dur­ing the mid 1890s was doc­u­mented in the book “Deer of Nova Sco­tia’ by Ben­son and Dodds (N.S. Dept. of Lands and Forests, 1977). The herd thrived and was re­ported in all main­land coun­ties by 1904. It first reached Cape Bre­ton around 1911. The healthy deer pop­u­la­tion was rapidly grow­ing just as the caribou pop­u­la­tion dis­ap­peared from the is­land. It may be co­in­ci­den­tal. How­ever, sci­en­tists pro­pose that moose, caribou and white-tailed deer can’t co-ex­ist in close quar­ters be­cause of a tiny brain worm with the sci­en­tific name of Pare­laphostrongy­lus tenuis. This par­a­site is com­mon in deer and they usu­ally show no ad­verse symp­toms. How­ever, P. tenuis is fatal for many other un­gu­lates such as caribou and moose. Caribou are now out of the pic­ture in Cape Bre­ton and the moose seem to be keep­ing a healthy dis­tance be­tween their pop­u­la­tions and those of the col­o­niz­ing white-tailed deer. Cur­rently we seem to be at an im­passe in the Bio­sphere.

So, why is the tiny brain worm tol­er­ated by white­tailed deer and not moose and caribou? And, why has it been more of a prob­lem in re­cent times? Well, white-tailed deer and P. tenuis have co-ex­isted for thou­sands of years and evo­lu­tion has en­abled the deer to adapt to this par­a­site. For the moose and caribou it is a rel­a­tively new threat and they haven’t had time to adapt.

Brain worm fa­tal­i­ties in moose and caribou are be­com­ing more of a prob­lem as the cli­mate warms. Warmer win­ters al­low the pop­u­la­tions of white-tailed deer and their tiny pas­sen­gers to move fur­ther north across North Amer­ica in­vad­ing tra­di­tional habi­tats of moose and caribou. An­other fac­tor re­lated to cli­mate change is in­creased rain­fall, which af­fects an­other player in this com­plex drama. The life­cy­cle of P. tenuis de­pends on the pres­ence of cer­tain species of snails and slugs which are the in­ter­me­di­ate hosts in the brain worm’s life­cy­cle. So, moist ecosys­tems with warmer win­ters have en­abled the white-tailed deer and their tiny brain worms to thrive and that may have contributed to the loss of the Bio­sphere’s caribou herds. What will hap­pen in the fu­ture in the snail and wor­m­me­di­ated im­passe be­tween the deer and the moose? Although we may place an ed­u­cated guess, it is hard to pre­dict. In na­ture, every­thing is con­nected and the na­ture of those con­nec­tions is of­ten very com­plex!

Dr. Annamarie Hatcher is an ad­junct pro­fes­sor at Unama’ki Col­lege, Cape Bre­ton Univer­sity, and a board mem­ber of the Bras d’or Lake Bio­sphere Re­serve As­so­ci­a­tion. For more in­for­ma­tion about the Bras d’or Lake Bio­sphere Re­serve As­so­ci­a­tion, please visit our Face­book page or http://blbra.ca/.

A white-tailed deer seen in the wild. File photo.

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