Bear Update: 

Transition to summer bear activity

Whistler Black Bear Project

Diet change = habitat use shift

Whistler black bears are beginning the summer transition period as they shift from grazing green-up (grasses, clover, horsetail, and dandelion flowers) to foraging carpenter ants ( Camponotus spp.) and ripening berries.

Diet change causes shifts in habitat use. Bears are beginning to leave open areas or corridors of green-up for timbered ridges, rock out-crops, and shrub-dominated patches. Grasses and clover are maturing and becoming too concentrated with cellulose for bears to digest efficiently. Ski area bears are following the progression of green-up to upper slopes where plants remain in the earliest stages of growth and cellulose is lower. The warmer spring (April-June) has bumped the diet shift about two weeks ahead of seasonal patterns.

Ants = protein

The single, largest source of protein for bears is carpenter ants and ant larvae. The ant feeding period begins in July and supplements the bear’s diet with protein before the major patches of berries are available.

Ants are found in rotten logs and tree stumps and under rocks. Bears will also forage ants near the foundations of houses. Observations have revealed bears ripping apart old wooden foundations that have been infested with ants.

Scats from ant feeding will have the appearance of black sawdust. Look closely and you may identify the tiny thoracic region of the ants’ bodies.

Bears also consume various nesting structures of bees and wasps. The honeycomb from bees’ nests are torn from subterranean nests between roots of second growth and mature growth coniferous trees in closed, dry forests.

Much ant foraging occurs in potential berry habitats. Tree canopy removal during logging, residential and recreational development, and wildfire all contribute to berry and ant habitat. Bears spend the day ant foraging while checking the availability of berries. Bears rely on ants more during periods of delayed berry ripening or periods of crop failures into September.

First berries

Bears began feeding on scattered early ripening of twinberries ( Lonicera spp.) and oval-leaf blueberry ( Vaccinium ovalifolium ) during the last two weeks of June. The shrub-dominated habitats along the Cheakamus River, Alta Lake Road, River of Golden Dreams, and Green Lake are active daily with bears.

Berries are not concentrated yet but their daily progression to ripening triggers bears to begin travelling through shrub and open forest habitats within residential areas. Berry ripening will progress with the sunny and warm weather. However, too much sun, leading to a potential drought this summer, could end the valley berry crop earlier. Berry phenology (development) is earlier for many species including important fall berries: high elevation huckleberry ( Vaccinium membranaceum ) and low elevation Sitka mountain-ash ( Sorbus sitchensis ) and red-osier dogwood ( Cornus stolonifera ). Cooler, wetter weather during summer and early fall would help stall berry crops until October.


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