Moose Hair Loss Survey
Moose showing moderate hair loss from vigorous licking, biting, or scratching to remove Winter Ticks.
Moose (Alces alces) are the largest animal in Algonquin Park and a crucial part of the ecosystem, but significant mortality-events of Moose have been associated with Winter Tick (Dermacentor albipictus) infestations in the past. Moose with heavy winter tick infestations groom vigorously by licking, biting, or scratching against a tree, which results in severe hair loss that can lead to decreased fat reserves, and in extreme cases hypothermia. Winter ticks (and the associated hair loss), plus normal winter coat shedding is what make Moose appear “scraggly” in the spring. To assess the severity of winter tick infestation, Algonquin Park staff have been conducting aerial Moose Hair Loss Surveys since 1984. An index is used to measure the severity of tick infestation based on the degree of hair loss, and make predictions about the potential impact to the local Moose population.
2013 Survey Results
Life stages of the Winter Tick (larvae on left, engorged adult female on right, adult male third from right)
The 2013 Moose Hair Loss Survey was conducted in Algonquin Park on March 23 and 24.
A total of 137 Moose were assessed for severity of hair loss, and ranked into one of five categories. The Hair Loss Severity Index (HSI) from this survey was calculated to be 1.88, which is slightly lower than the average HSI (1.90) over the history of the survey (1984-2012). A below average HSI is not associated with winter tick related mortality events, and a significant effect on the Moose population is not expected this year. This result was not anticipated based on the current moose population and previous spring temperatures, both of which thought to be favourable for tick populations. Generally, an early spring (like the one we witnessed in 2012), late fall, and relatively high Moose population bodes well for the ticks.
Why Were There Not as Many Ticks As Expected This Year?
Embedded female Winter Ticks measuring about the size of a grape.
Without a detailed study it is difficult to say for sure, but there could be a number of environmental factors at play. First of all, 2012 was definitely a year of weather anomalies – not only did it have the earliest ice-out date on Lake Opeongo in the history of our records, but March actually had a warmer average temperature than April (according to Environment Canada), which is highly unusual! Warm spring conditions with no snow are supposed to be very favourable for the female ticks when they drop off the moose, full of blood and ready to lay eggs. However, you might also recall that April had some very cold temperatures with a hard frost late in the month, which we know affected the blossoms on fruit trees, and may have also had a negative impact on tick eggs. But the other major weather anomaly that we witnessed in 2012 was the drought. By late July there were extreme fire indices, and a drought that caused Algonquin Park to impose a Restricted Fire Zone (fire ban). This may also have an impeded the growth of the tick population, as droughts have been shown to affect other tick species. A combination of these factors may have limited tick numbers in 2012, or it could be something altogether different that we have not documented yet. Until research looks further into how Moose, ticks, and weather interact, consider it a natural history mystery!
Algonquin Park staff are always interested in the health of the local Moose population and we would be particularly interested in any sightings and pictures of moose with hair loss this spring. If possible, please send your observations along with the time, location, number of moose, male/female, adult/calf, % hair loss, a picture (if possible), and any other valuable information.