Projection of Woodland Caribou Populations in Newfoundland
An application of Leslie-Matrix population models to predict the future of Newfoundland Caribou Herds (2010-2035)
Sustainable Development and Strategic Science
- The woodland caribou population on the island of Newfoundland has declined by more than 60% since the mid-1990s. Several individual herds have declined more than 90%. Overall, these declines have created a concern for the future status of caribou in Newfoundland.
- A five-year Caribou Strategy was launched in 2008 by the Government of Newfoundland and Labrador to conduct an ecosystem-level analysis of caribou population dynamics. Research activities included investigations into caribou demography, morphology, predator-prey dynamics, spatio-temporal habitat use patterns, and human dimensions.
- This report describes efforts to use mathematical models (matrix projection models) to assess the likely future status of caribou populations in Newfoundland. The models considered a) the island-wide population, and b) individual herds, using long-term demographic data.
- Radio-telemetry data and aerial surveys indicated that annual calf survival in the past decade was dramatically lower than in previous decades, while most other age classes have remained relatively stable. Poor calf survival has resulted in:
i. a numerical decline in the caribou population, and
ii. a steadily aging breeding population that is not being replaced, also known as the Demographic Wave issue.
- The models developed in this report considered a range of scenarios related to calf survival including the continuation of low survival rates, as well as a return to pre-decline levels of survival.
- Herd age classification data, and model projections indicate that the Demographic Wave has largely passed through the herd by 2011. This suggests the age structure of the population is likely not a concern with respect to population trajectories, assuming that adult reproductive ability is independent of age.
- The models indicate that a continuation of low calf survival into the future (i.e., the status quo) would result in a further 90% decline in the Newfoundland population over the next 25 years. Similar patterns were observed for individual herds.
- However, if annual calf survival increases to between 40 and 55%, there exists a strong likelihood that the population decline will be halted or reversed. These rates have been observed previously in Newfoundland calves and are therefore within the realm of possibility as a management objective.