Temperature certainly has an effect on batteries¹. But also that the periods of high current demand were spaced so far apart -- the batteries had time to recover. Much like how the battery in your car is a "starting" battery -- high current is needed only occasionally to start the engine, with the alternator making up the demand the rest of the time.

¹ Dad used to work for Union Carbide, which owned the "Eveready" brand at the time. One of the projects he worked on was a battery for the Union Pacific Railroad. It was designed to be buried in the ground in remote locations to run signal systems. Burying it gave it a more constant temperature. If the researchers placed the battery on the inside of the collar next to the wolf's fur, that could really extend it's life.