Big Game Aerial Surveys

Winter aerial surveys are one of the primary tools Manitoba Sustainable Development uses to collect important information on many of Manitoba’s big game populations.  Biologists use information from surveys, such as density of animals and sex and age composition, to aid in the assessment of the overall status of a big game population - moose, elk, white-tailed deer, gray wolf and barren ground caribou.  Every year, wildlife managers must determine which populations are to be surveyed by aircraft.  Surveys for moose, elk, white-tailed deer and gray wolves are generally conducted by Game Hunting Area (GHA).

In most years, there is a greater need for surveys than there are funds available.  The Wildlife and Fisheries Branch allocates big game survey program funds on a priority ranking basis. Survey needs for the entire province are ranked annually and the highest ranking surveys are funded from that ranked list.  When determining the rank, the following factors are considered:

  • reason(s) to believe a change has occurred in the population
  • public interest
  • population is subject to high use
  • provide baseline or update data for appropriate management
  • environmental change
  • landscape development

Currently, the department's budget allows for four to five surveys to be completed on an annual basis. Suboptimal conditions may prevent flying a high priority survey area. If this occurs, the department will attempt to replace this survey with another survey.

In 2018, the province plans on conducting the following surveys, presented in order of priority, as budgets and conditions (see limitations below) allow:

  • GHA 7 - moose - Northwest Region
  • GHAs 18, 18A, 18B, 18C (Duck Mountain) - elk - Western Region
  • GHAs 21, 25, 25A (South Interlake) - elk - Central Region
  • GHA 17A - moose - Eastern Region
  • GHAs 15, 15A - moose - Central Region
  • GHA 26 - moose - Eastern Region
  • GHAs 16 and 20 (North Interlake) - elk - Central Region
  • GHAs 29, 29A (Turtle Mountain) - deer, elk, moose - Western Region
  • GHAs 35, 35A - elk - Eastern Region

Limitations

  • A minimum snow depth of 25 cm is required for the entire survey area.
  • Temperature cannot be below -30°C.
  • Aerial moose surveys are typically flown in January while elk and white-tailed deer surveys are flown in February.
  • Safe flying conditions.

Survey Methods and Assessment of Population Status

Aerial surveys are the most reliable method for indexing most big game populations over large areas. Repeated aerial surveys allow biologists to determine changes in population trend over time and evaluate changes in sex and age ratios. The collection of high quality data allows biologists to communicate results with confidence and provides insight into the effectiveness of management actions.

Biologists need to compare aerial survey results through time to monitor population trends and they rely on methods that are repeatable and consistent. Methods used to monitor big game populations in Manitoba vary based on factors such as the target species and the density at which the species occurs. A stratified random block design (see Gasaway et al. 1986 for more information) is a big game survey method used by many jurisdictions, including Manitoba. The stratified random block survey is made up of two parts; a stratification survey followed by intensively sampling of a subset of randomly selected blocks.

Stratification Survey - The intent of the stratification survey is to assign strata (based on perceived animal density, typically: ‘high’, ‘medium’ and ‘low’) to sample blocks within the survey area. One of the most important factors influencing the precision of results in a stratified random block survey is how well an area is stratified. Only experienced biologists are used during the stratification survey to ensure consistency of results. Information, including the number of animals detected and density of tracks, collected along survey transects are used to assign perceived animal density of each sample block relative to another within the survey area. In Manitoba, the stratification survey accounts for a little less than half of the overall duration of the survey. It is critical to ensure the best possible stratification is obtained to allow biologists to better detect changes in population size.

Intensive Sampling - Strata are determined following the stratification survey, after which intensive sampling takes place. The intensive sampling portion of the survey involves a count of the number of animals observed within randomly selected blocks within each strata. In general, ~20% of the entire survey area is intensively sampled. The goal is to count all animals in the sample block, but this may not always be possible. There are factors that affect how easily big game animals are detected from the air and survey methods are standardized to minimize many of these factors. For example, during winter surveys, it is easier to detect animals when snow is deeper and therefore, a minimum snow depth is required before a survey can be conducted. This also ensures that successive surveys are conducted under similar minimum conditions allowing better comparison of results between years.

Analysis - After the survey is completed, data are carefully checked for accuracy and the total number of animals detected in each block sampled during intensive sampling are used to produce a density estimate for each strata. These strata-specific density estimates are then extrapolated to the entire survey area to produce a point estimate with statistical confidence limits (which reflect the precision of the estimate) for the survey area. This estimate (and associated confidence limits) can then be compared to previous survey results providing the same survey methods were used. Estimates produced provide indices of population size rather than true population estimates, which are more costly both in time and resources. Comparing estimates between years allows biologists to monitor whether the population is increasing, decreasing, or stable. Additional information obtained during aerial surveys of moose are age and sex ratios which can provide additional information of the status of the population.

Survey Results from 2016-17

Survey Results from 2015-16

Survey Results from 2014-15

Survey reports from the 2017 survey season will be available online as they are completed. Data will be available by request as reports are completed.

Literature Cited Gasaway, W.C., S.D. DuBois, D.J. Reed, and S.J. Harbo. 1986. Estimating moose population parameters from aerial surveys. Biological Papers of the University of Alaska; no. 22.