Caribou Calf Mortality Study 2003-2007
Caribou populations are declining globally. Newfoundland’s caribou population is not designated as "At- Risk", but they have declined from nearly 100,000 animals in the late 1990s to just over 38,000 animals in 2008. Population modeling suggests that Newfoundland caribou could be assessed as "At-Risk" by 2012. Ongoing research and monitoring efforts suggest that the population decline was partially attributable to high levels of calf mortality. The Calf Mortality Study (2003-2007) was initiated to empirically identify the causes, rates, and timing of calf mortality in three herds: the Middle Ridge, Gaff Topsails, and Mount Peyton.
The study was conducted by the Sustainable Development and Strategic Science Branch (Department of Environment and Conservation) of the Government of Newfoundland and Labrador. The Calf Mortality Study has shown that:
- Annual survival estimates for neonate calves were extremely low (4% survival) when compared to historical estimates (66% survival), in particular for those calves at Middle Ridge.
- Predation by bears, coyotes, lynx and eagles was the single greatest cause of calf mortality across herds and years.
- The importance of different predator species varied among herds. At Middle Ridge, black bear were primarily responsible for calf mortalities. At Gaff Topsails, eagle and coyotes caused the most mortalities, while lynx were most important in Mount Peyton.
- Predator-caused calf mortality events occurred primarily during the first eight weeks of calf life, especially in the first four.
- Survival estimates of calves from 6-months to 1-year (i.e. overwinter) were 87% and comparable to adult survival. Contrary to anecdotal reports, overwinter mortality was not found to be a significant contributor to calf mortality.
- The weight of calves at capture had no influence on survival.
These results, combined with the Caribou Data Synthesis, form the basis of the Newfoundland Caribou Strategy. The Strategy is another five year effort to identify the factors underlying the extremely low calf survival and the caribou population decline.