Ecology and Vulnerability

Moose

Background
The moose is a cold-adapted species that is distributed across much of the northern United States and throughout Canada, as well as Europe and Asia.  A dense coat and large body size help moose deal with extremely cold temperatures.  They spend much of their time foraging on the buds, stems, and occasionally bark of woody vegetation throughout the year, as well as newly growing green shoots and leaves in the spring.  Because they are so big, moose require a large volume of food, and some individuals consume more than 40-60 pounds of forage in a day.

In eastern North America, moose are at the southern limit of their range in Massachusetts and Connecticut¹. Historically, they were found as far south as Pennsylvania and New Jersey, but were extirpated (went locally extinct) from these states and southern New England during colonial times.  Currently, southern New England appears to have a healthy, relatively stable moose population, despite the recent dramatic declines seen elsewhere, such as in Minnesota.

Climate Impacts
Moose populations in Massachusetts are at low densities and do not appear to be declining².  Likewise, sightings in Connecticut have been increasing³.  Conditions in Massachusetts are currently favorable for moose because thermal refuges, such as wetlands and closed canopy forest that allow moose to remain cool during hot days, are well interspersed with young, vigorously growing forest, which is their main forage habitat.  Interactions with white-tailed deer, which can act as carriers for diseases to moose, do not seem as harmful to moose in Massachusetts, probably because the moose population itself is not very dense.  In addition, lack of important predators, such as wolves, reduces overall mortality and allows moose to remain in food patches and thermal shelters for longer periods of time, rather than being pushed and moved by predators, which can increase energy demands and thermal stress².  However, given increased temperatures associated with future climate change scenarios, several experts predict moose distributions will retreat northward^4,5,6. 

In southern areas, moose experience heat stress and demonstrate behavioral responses to elevated temperatures^7,8.  In contrast to Massachusetts, several of these southern populations are currently declining, including populations in Minnesota⁹, Nova Scotia⁷, China⁴, and southern Norway⁸.  Studies have linked these declines to changes associated with climate change, including increased densities of winter tick (Dermacentor albipicuts), and perhaps other parasites such as meningeal worm or brainworm (Parelaphostrongylus tenuis) carried by growing white-tailed deer populations; the stress of trying to maintain body temperature (thermoregulation) given rising air temperatures may also play an important role^4,9.

Moose are susceptible to infestation by winter ticks and extreme tick loads are associated with substantial mortality¹⁰.  Moose burdened by tick infestations rub against objects to relieve irritation, resulting in hair loss.  Severe winters can greatly reduce tick survival, but the milder winters predicted are expected to increase tick densities.  This increase in ticks is likely to result in increased mortality of moose in the Northeast¹¹.