From a reader:

Maybe Cosmo should stop harassing squirrels: They were on our side during the Cold War. The following is from a 1961 GRU (Soviet Military Intelligence) training manual titled “Characteristics of Agent Communications and of Agent Handling in the U.S.A.” (reprinted in The Penkovsky Papers, which I’m reading at the moment):
“In selecting and preparing a dead drop in a park, one must bear in mind that a number of American parks (for example, Central Park in New York) have many squirrels which can destroy the dead drop (especially in hollow trees) and carry off our material.”