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Talking Moose Ticks with Dwayne Sabine

A major threat to the moose population in our province in recent years have been the winter ticks, and some areas have seen their population take a serious hit from deaths due to these ticks. These moose are known as “ghost” moose because the white base of hair shaft is all that remains. Scientists are trying to study why these deaths are occurring more frequently in recent years as the two species have coexisted perfectly fine for thousands of years. They are a native parasite, and parasites should not be fatal to their hosts. However winter die-offs from ticks are increasing across North America.  The winter tick grows to an impressive size of up to 15mm, peaking toward the end of winter. When infestations are significant, thousands of ticks can attack a single moose. Studies by the University of Alberta indicate that if a calf is infested by 30,000 ticks they must replace nearly 60% of their blood volume in March and April. An infestation of 70,000 ticks forces the moose to replace 112% of their blood volume in the same time frame. Moose infested by this volume of ticks will lose between 40 and 100% of their insulating hair leaving them at risk of hypothermia. They also become preoccupied with grooming to try to deal with the itching, which can put them at greater risk of predation. Time that is better spent resting or feeding is instead focused on licking, rubbing, and scratching. If the moose is heavily infested with ticks, they can exhibit abnormal behaviour, suffer weight loss and hair loss, loss of blood, poor physical conditions. The cumulative effects of all these symptoms can make them more vulnerable to predators and severely affected animals may die. In the winter of 2013-14 it was thought that perhaps as much as half the moose population in zone 20 of New Brunswick may have died, and experts say the majority were from winter tick infestations.  Moose harvest allotments show a similar trend, with zones like 20 and 23 adown as much as 50% since 2010.

Dwayne Sabine has a job many of us would dream of, being Wildlife Biologist, Big Game, Furbearers, and Fisheries, but it's not always as much fun as you might think. Certainly, he gets to take part in the annual NB moose count done by helicopter giving an indication of the population and health of the herd. But with the passion of hunters and outdoor fanatics across the province, the position comes with a great responsibility. Being one of the faces of the province in terms of big game populations is not something he takes lightly, and you can tell he loves his job despite the often public nature of it. Everyone seems to have an idea of how to better manage the herd and with a draw where over 90% of moose draw applicants don't receive a license there are bound to be many passionate opinions. We are very thankful for the opportunity to sit down with him and discuss the state of the herd at a time that he is extremely busy.

Wilderness Obsession:  We read an article that said perhaps as much as half the moose population in WMZ 20 of New Brunswick had died in the winter of 2013-14, and experts said the majority were from winter tick infestations. Can you confirm this and how has the population in WMZ 20 done since then?

Dwayne Sabine: The estimated moose population in WMZ 20 has dropped by 50% over the past 10 years (2007-2016).  Several other WMZs in extreme southern NB have experienced similar rates of decline.  The cause is not entirely certain, but given the relatively short time-frame of declines, and because relatively high rates of visible tick infestation have been noted during recent aerial moose surveys, and based partly on the findings of recent studies in northern New England, winter ticks are suspected as the probable cause.

Wilderness Obsession: What type of tick is infesting our New Brunswick moose? Is this a recent trend or something that has infested our moose for a number of years?

Dwayne: The tick affecting NB moose is the winter tick, sometimes called moose tick, Demacentor albipictus.  This tick species is found wherever white-tailed deer, the primary host, are found, and have probably affected moose as long as there have been deer in the province.

Wilderness Obsession: How could a winter tick infestation possibly kill an enormous moose?

Dwayne:  Heavy infestations of winters ticks may cause moose mortality primarily through the effects of anemia (essentially blood loss due to feeding by ticks), reduced ability to regulate body temperatures due to hair loss (caused by moose attempting to groom or rub ticks off their body), and reduced feeding time by moose due to increased time spent grooming ticks (resulting in less energy intake at a critical time of year).  Due to the unique life cycle of the winter tick, all of these impacts occur during winter, the most physiologically-stressful time of year for moose and other affected ungulates in northern climates.

Wilderness Obsession: Does the department keep stats of the number of moose they believe may have died from winter tick infestations? Are there any stats that you can share with us?

The lifecycle of a winter tick

Dwayne:  It is very difficult & resource intensive to collect data on cause-specific mortality rates for wildlife populations.  The Departments does not have data on mortality rates of moose due to tick damage.

Wilderness Obsession: If the belief is that a moose has died from tick infestation, what sort of studies can you do to find out more information about the specimen and cause of death?

Dwayne: Determining a definitive cause of death for moose, whether due to ticks or any other causes, would require necropsy immediately following death of the animal, before the carcass is found by scavengers or has started to decompose.  That, in turn, generally requires that a sample of animals be captured, outfitted with a tracking device, and continually monitored to determine when death occurs.  This is the type of project currently underway in Maine and New Hampshire.

Wilderness Obsession: We have seen a number of pictures posted online of moose that look nearly white from hair loss. Is this natural for this time of the year, or would these be from tick infections? (and the heavy grooming/scratching leading to broken/lost hair)

Dwayne: It is not normal for moose to lose patches of hair during this time of year.  Moose begin moulting into their new coat of hair each spring, which involves the gradual replacement of old hair with a new set, progressing over the body, and can give them a somewhat shaggy appearance.  However, extensive hair loss, often seen on the front shoulders and hump, and sometimes over the majority of a moose’s body, is typically the result of excessive grooming and rubbing of moose trying to rid themselves of winter ticks.  Moose with very extensive hair loss due to rubbing will appear white or light gray, as only the light-coloured base of the hair remains on the animal.  These are sometimes called “ghost moose”.

Wilderness Obsession: We wrote an article two years ago and quoted biologists who told us that moose and these ticks have coexisted fine for thousands of years. Is this correct, and as a biologist, do you have any idea why a native parasite like these winter ticks have begun having a fatal effect on moose?

Dwayne: Winter ticks are thought to have co-evolved with white-tailed deer, and occur anywhere in North America where white-tailed deer are found.  They only affect moose populations in or near areas where moose are sympatric with white-tailed deer.  That area of overlap has expanded since European settlement as white-tailed deer distribution has shifted northward.  Moose populations in eastern Canada have varied considerably since the 1800s.  It is possible that some local declines in the past

Wilderness Obsession: Provincial deer biologist Joe Kennedy mentioned to us in an interview that the changing climate (generally warming) is likely have make our province more hospitable for whitetail deer. What kind of an effect might you expect a warming climate to have on our moose, and why might that be?

Dwayne: Winter tick populations are thought to be strongly affected by spring and fall weather conditions.  Female ticks drop from their moose and deer hosts to lay eggs on the forest floor in the spring.  Cold, late spring conditions with snow cover present on the ground later than usual is thought to result in reduced survival of these egg-laying females, and thus decreased winter tick populations the following winter.  The larval ticks ascend vegetation to attach to moose and deer in the fall.  Colder than usual fall weather conditions and early onset of winter is thought to reduce the period of time for this to occur, thus resulting in decreased winter tick populations during winter.  Any long-term trend towards warmer spring and fall climates would presumably be beneficial to winter tick populations.

This pattern may also explain why the moose population declines in NB appear limited to the warmest part of the province in the extreme south, while moose population in northern NB, which experiences a colder climate, have increased in recent years.

Wilderness Obsession: Maine is in their third year of a study on moose mortality where they have radio collared moose and investigated any deaths immediately. We also know that New Hampshire is doing the same sort of study. Is any study of that nature ongoing in New Brunswick? Do you know of any provinces in Canada that are undertaking a study into winter tick mortality?

Dwayne: There is not any study of that nature occurring in NB at this time.  I have no information on whether university researchers in other provinces are studying moose and winter ticks.

We would like to thank Mr. Sabine for taking the time to sit down with us today to discuss the Moose Population in NB and what might be causing the population drops we’ve seen.

As mentioned above, the states of Maine and New Hampshire have been investigating whether it might be the combination of heavy winter tick infestations along with possible “lungworm” infections that are causing the heavy winter-tick mortality. A lungworm is a nematode causing bronchitis and lung lesions. The combination of these two problems could be simply too much for their system to take, and are making them vulnerable to die from the parasite and disease.

Although we don't yet have a definitive answer on why the winter ticks have begun having this effect on moose across the continent, biologists are putting a great deal of effort into figuring it out. Since the 1900s, the moose population has dropped in almost every area of North America, some very dramatically. Moose hunting is an enormous industry and states and provinces alike are interested in protecting their revenue. Hunters and outdoor obsessed individuals should be hoping for their success, as a world without these majestic creatures would be a sad one indeed.

2016-06-08 19:04:40

 

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