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BC Moose Population Research Project

From the Sept/Oct issue

by Brian Harris

Moose (Alces alces) are an important game animal in BC. They are found from the US border to the Yukon and absent only from the mainland coast and the coastal islands. In central BC the forested plateaus, studded with lakes and ponds, have held some of the highest moose densities on North America. However, starting 10 or so years ago, hunters in the parts of Cariboo, Skeena and Prince George Fish and Wildlife Regions reported increasing difficulty in finding moose. These reports triggered a major inventory effort and were confirmed by moose aerial surveys undertaken by BC Government wildlife biologists. In some surveyed areas, moose numbers were down by as much as 70% since the previous inventory. This decline appeared to coincide with the massive mountain pine beetle (MPB) infestation in the lodgepole pine forests of central BC and the accompanying salvage logging and road building.

In 2013, concern about this decline of moose numbers and its cause prompted the Ministry of Forests Lands and Natural Resource Operations to initiate what is likely the most extensive moose population study in North America. A five-year research project will test the landscape change hypothesis (i.e. the impact of MPB infestation and logging) by identifying the causes and rates of cow moose mortality and examining the factors that contributed to their vulnerability. The survival of adult cows is the most important factor determining moose population change.

In each of five study areas, a minimum of 30 GPS radio collars have been deployed on adult cow moose. For the Kamloops study site, this capture and collaring started in February 2012, but elsewhere, the study started in the winter of 2013/14. The animals were captured using either tranquillizer darts or net guns, and biological samples to identify diseases and pregnancy were collected when the collars were attached. Currently (May 2015) there are 175 collared moose in the study areas. A collar that hasn’t moved in four to12 hours is likely attached to a cow that has died. In that case, a mortality alert and the location is emailed via satellite from the collar to the research team computers. Prompt field investigation of the mortalities is important to determine the cause.

It is early in the study, but there are some preliminary findings.

  • Overall average pregnancy rate from a sample of 217 cows was 78%. This is slightly lower than the North American average of 84%.
  • No significant disease issues were identified.
  • Of the 19 mortalities investigated:
    • Nine killed by wolves,
    • Three from unregulated hunting,
    • Three starved,
    • One vehicle collision
    • Three from unknown natural causes.
  • In a stable moose population, at least 85% of the adult cows survive year to year. The annual survival rates in this study have been:
    • 2012/13: 95%
    • 2013/14: 88%
    • 2014/15: 95%

With some collars only recently deployed, it is still too early in the study for definitive results. However, general interpretations of the data so far are that:

  • The overall adult cow survival rates are consistent with a stable population.
  • There is nothing alarming about the causes.
  • The three starvation mortalities are interesting because this was not anticipated to be a significant cause of death.

So the search for the culprit in the widespread moose population decline in central BC continues. Unfortunately, even with the effort of this big inventory and research project, there may be other factors affecting moose productivity that are not yet being investigated.

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