A determined squirrel which chewed its way into a substation at the Whitehorse Rapids Dam was behind Monday's blackout which left many wishing they'd packed a lunch.

Just before noon, the Yukon's tiniest furbearer knocked out power to some 14,495 customers from Faro to Teslin, Pelly Crossing to Haines Junction.

The 950 customers in rural communities, with the exception of Haines Junction, had power restored within five minutes by their back-up diesel generators.

But most of Whitehorse was out for more than an hour.

Yukon Energy spokeswoman Janet Patterson said today the squirrel chewed through a wooden animal protection barrier meant to keep rodents out of the substation at the Whitehorse dam.

"So what we are doing now is looking at what else might be put there that would keep small animals out,” she said. "How could one little squirrel take out the whole grid?

"It was because it was our main hub basically. When that was taken out, we lost all our Whitehorse hydro generation and Aishihik (hydro facility) could not meet the load, and that's why we lost the whole system.”

Patterson said animal protection barriers are in place at all substations.

Once the squirrel got inside, however, there were cables and such that are susceptible to curious rodents running around, she explained.

The entire Whitehorse-Aishihik-Faro grid went down.

There was no disruption to the Mayo-Dawson grid, which is still separate but is scheduled to be tied into the main grid by mid-June.

Downtown Whitehorse was the first section of the city to be powered back up just under an hour later, at 12:56, when the lunch bunch was heading back to work. Most of the city was back up between 1:25 and 1:35 p.m.

The lines to Carcross and Teslin were re-energized at 1:43, while Carmacks, Faro and the Minto mine were returned to grid power at 1:31.

Patterson said a check of the substation did find the dead squirrel. It was the second system-wide outage of the WAF grid this year.