Male and female rats may have sex twenty times a day. A female can produce up to twelve litters of twenty rats a year: one pair of rats has the potential for 15,000 descendants in a year.
In certain species of seals, like the elephant seal, males may be several times larger than females because larger males can better defeat their rivals in territorial fights and so acquire larger harems.
Squids are a large, diverse group of marine cephalopods. They begin mating with a circling nuptial dance, revolving around across a `spawning bed' (200 metres, in diameter). At daybreak, they begin having sex and continue all day long --they only take a break so the female can drive down and deposit eggs. When she returns to the circle, the two go at it again. As twilight falls, the pair go offshore to eat and rest. At the first sign of sunlight, they return to their spot and do it all over again.
Penguins in general prefer to be `married', but they suffer long separations due to their migratory habits. When reunited, a pair will stand breast to breast, heads thrown back, singing loudly, with outstretched flippers trembling. Two weeks after a pair is formed, their union is consummated. The male makes his intentions known by laying his head across his partner's stomach. They go on a long trek to find privacy, but the actual process of intercourse takes only three minutes. Neither penguin will mate again that year. The male Adele penguin must select his mate from a colony of more than a million, and he indicates his choice by rolling a stone at the female's feet. Stones are scarce at mating time because many are needed to build walls around nests. It becomes commonplace for penguins to steal them from one another. If she accepts this gift, they stand belly to belly and sing a mating song.
There is a common joke: "How do porcupines do it?" "Very carefully." But in reality, the truth is more bizarre than dangerous. Females are only receptive for a few hours a yearm, so they go off their food, and stick close by the males and mope. Meanwhile the male becomes aggressive with other males, and begins a period of carefully sniffing every place the female of his choice urinates, smelling her all over. This is a tremendous aphrodisiac. While she is sulking by his side, he begins to `sing'. When he is ready to make love, the female runs away if she's not ready. If she is in the mood, they both rear up and face each other, belly-to-belly. Then, males spray their ladies with a tremendous stream of urine, soaking their loved one from head to foot - the stream can shoot as far as 7 feet. It is advised never to stand close to a cage that contains courting porcupines.
Red-sided Garter snakes are small and poisonous, and live in Canada and the Northwestern United States, and they prefer orgies. Their highly unusual mating takes place during an enormous orgy. Twenty-five thousand snakes slither together in a large den, eager to copulate. In that pile, one female may have as many as 100 males vying for her. These `nesting balls' grow as large as two feet high. Now and then a female is crushed under the heavy mound - and the males are so randy that they continue to copulate, becoming the only necrophiliac snakes!
Anglerfishes are bony fishes. Some of them have a unique mating method: Since individuals are rare and encounters doubly so, finding a mate is a problem, especially at a time when both individuals are ready to spawn. When a male anglerfish hatches, it is equipped with extremely well developed olfactory organs that detect scents in the water. They have no digestive system, and thus are unable to feed independently. They must find a female anglerfish, and quickly, or else they will die. When he finds a female, he bites into her flank, and releases an enzyme which digests the skin of his mouth and her body, fusing the pair down to the blood vessel level. The male then atrophies into nothing more than a pair of gonads that release sperm in response to hormones in the female's bloodstream indicating egg release. This is an extreme example of sexual dimorphism. However, it ensures that when the female is ready to spawn, she has a mate immediately available.
The female mite known as Histiostoma murchiei creates her own husband from scratch. She lays eggs that turn into adults without needing to be fertilised. The mother then copulates with her sons within three to four days of laying the eggs, after which the sons die rather quickly.
In Maryland, it is illegal to sell condoms from vending machines with one exception: prophylactics may be dispensed from a vending machine only "in places where alcoholic beverages are sold for on the premises."