Saturday, February 28, 2015

Vaginal implants and other moose study facts

While reading studies about moose this winter I came across some really fascinating techniques and findings of biologists. Right at the top of the list was a study called Moose Calf Mortality in Central Ontario (Patterson, 2013).
Other studies done decades ago in Alaska had found that black bears may be the largest predators of moose because they consumed up to half of the calves, almost immediately after the calves were born in the spring.
At Bow Narrows Camp we have seen this exact predator-prey scenario unfold many times -- cow moose swimming out to islands to give birth and then bears swimming out to the islands and then the cows and the new-born calves swimming away from the islands on the other side. It has been impossible for us to tell how many of the calves the bears actually killed and biologists anywhere in densely forested Ontario have had the same problem. In the open country of Alaska, you can spot the moose and the bears from the air. That technique just won't work here with our continuous and thick canopy of trees.
So, in the Patterson study, biologists put vaginal implant transmitters (VITs) in 99 cow moose in Algonquin Provincial Park and Wildlife Management Unit 49. The cows were also fitted with tracking collars. When a cow gave birth, the VIT was pushed out of the birth canal and it then sent a signal to the researchers that the calf had been born so that they could quickly fix a radio collar on it and track its movements. If the calf stopped moving, like when it was killed, the collar sent out a signal and the researchers could again quickly examine the remains to see what killed it. Pretty ingenious!
The study found that bears killed about the same percentage of calves in the spring as wolves do in the winter. Between them they got 28 per cent of the calves.
It also found that 20 per cent of the cows in the park gave birth to twins but outside the park that rate was just 12.5%, probably due to poorer habitat as the researchers also found malnutrition and tick mortality was four times greater in WMU 49.
There was evidence in a study done in Manitoba that black bears can have a bigger impact on moose calves in some situations. This study was done on Hecla Island in southern Lake Winnipeg. Hecla at one time had such a dense moose population it was called the Isle Royale of Canada. (Isle Royale in Lake Superior is the location of the longest-running wildlife study in the world. Just about everything known about the relationship of moose and wolves comes from that study.)
A combination of factors was believed to have contributed to a decline of Hecla Island's moose population, to just 25 individuals in the year 2000, down from 221 in 1979. But researchers believed the building of a causeway to the island was a prime factor because it gave bears better access. As far as anyone could tell, there were no bears on the island in 1979, before the causeway, and there were 20-30 bears in 1999.
Winter aerial surveys in 2000 found that there were no moose calves at all. Back in 1979, the calf/cow ratio had been 46 calves per 100 cows.
So in an experiment in 2002, researchers live-trapped and removed 12 bears from the island. That was roughly half of the bears there. The next year they found that the calf/cow ratio jumped immediately to 40/100.
The researchers also noted other studies, one in Saskatchewan where 12 bears were removed from a 90-km2 area and the ratio jumped to 80 calves/100 cows, up from 40 in a control area.
Research has also shown that the killing of moose calves by bears in the spring is mostly done by large, male bears. As one biologist pointed out, these are the same type of bear that have caused almost all of the attacks on humans. They didn't mention it but it is also the very bears that were highly sought by hunters when Ontario had a spring bear hunt. It has always been illegal in Ontario to shoot a mother bear with cubs. That was the case when we had spring bear hunting and it is still the case now that there is only fall bear hunting. However, female bears are very much smaller than the males, so hunters never wanted them anyway.
Incidentally, the Hecla Island study found the moose calf twinning rate there was 28 per cent.
Research quoted in the study speculated that predation by both bears and wolves on moose was a greater factor when moose were already at low densities. That could be particularly relevant in Ontario which is seeing its moose population plummet, mostly, it seems from brain worm parasites transmitted by whitetail deer.
I was at a moose seminar at the Northern Ontario Tourism Summit in November in Thunder Bay and asked a biologist from the Ministry of Natural Resources and Forests if he agreed that whitetail deer and brain worm were the largest reason moose were disappearing. He said no, he couldn't agree because moose were expanding in southern Saskatchewan and the U.S. Northeast, both places which also have good whitetail populations.
Well, the studies I found explain why that could be the case. As mentioned in the previous blog posting, brain worm goes from deer poop to gastropods -- snails and slugs -- to moose. Southern Saskatchewan is a prairie with very little rainfall. There would be very few snails and slugs there.
And in the U.S. Northeast, acid rain, both currently occurring and from the past, has made the soil too acidic for gastropods. Biologists there have stated that acid rain is likely what is saving their moose.
Meanwhile in Northern Ontario, climate change is making the summers wetter and even better for gastropods, hence the rapid transmission of brain worm from deer to moose.
Studies in Manitoba show 100 per cent of the deer there have the parasite which is harmless to them, harmless to humans, and fatal to moose. In Grand Marais, Minnesota 90 per cent of the deer were found to have brain worm. Grand Marais is very near Thunder Bay, Ont. and Wildlife Management Unit 13 which has seen some of the largest declines of moose in the province.
Advice from a game manager in Grand Marais, if you want to save the moose "hammer the deer as hard as possible."
A perplexing study done in Quebec, way back in 1978 -- before Ontario even had a selective harvest system -- found that moose calves that were orphaned had the same survival rate as those that were raised with their mothers. This flies in the face of observations and advice of Ontario's moose managers that went to great lengths in 1982 when we started our selective harvest system to explain that a calf needs its mother to teach it survival skills in the winter. Therefore hunters who had cow tags and came across a cow with a calf, should harvest the calf and let the cow go. To shoot the cow and not the calf was the same thing as killing two moose, they preached. Now, one of the options being floated by the MNRF is to do that very thing -- kill the cow and let the calves go. That's because they want to see more calves in the winter population.
What I noticed is that the Quebec study only followed 28 calves. The sample size was so small that I have a hard time believing the results. And I personally have never seen or even heard about a moose calf surviving the winter alone.
Just for comparison purposes, here are some interesting current facts on wildlife populations in Ontario and Quebec.
Ontario: deer 400,000, moose 105,000, bear 85,000-105,000, wolves 9,000.
Quebec:  deer 367,000, moose 125,000, bear 70,000, wolves 7,000.
What jumps out at me is that Ontario has more deer, fewer moose, more bears and more wolves.

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