breeding males may also advertise honestly to warn rival males of their strength, a classic example being the red deer, where the roaring of a rutting stag reliably signals its size. the honest advertisement benefits both sender and receiver, as neither need become involved in a costly fight to assess their relative strength. in the breeding season, frogs congregate at suitable breeding sites and call to advertise their presence, particularly at night. females can distinguish between the fitness of males based on the characteristics of their voices. desert toads emerge from their burrows in response to heavy rain. males emerge first and when one finds a suitable ephemeral pool, its call attracts others and they all congregate there. males may call in unison in noisy choruses, and breeding is explosive, a mass of males competing for the smaller number of females.