Chapter 5 (Part A): Male Reproductive Behavior

1. Chapter 5 (Part A): Male Reproductive Behavior (Note: Chapter 6 covers Female Reproductive Behavior)

2. In this chapter, we examine the hormonal aspects of males that leads to their particular reproductive behaviors. Topics of focus include the examination of:

3. Territoriality in elephant seals. The fights erupt as males guard prime locations in terms of resources.

4. 5.2 Male sexual behavior Proximate basis of male sexual behaviors can be subdivided as follows: Appetitive phase – the period when the male is actively seeking sexual encounters Consumatory phase – the period when the male is actively engaged in copulation

5. Charles Edouard Brown-Sequard – endocrinologist who in the late 1800s proclaimed extracts of testes injected in the body had rejuvinating effects on sexual behavior..

6. 5.4 Testosterone treatment maintains sexual behavior after castration Sexual behavior can be maintained in animals following castration via replacement testosterone. Note that there is a threshold dosage of testosterone that is needed.

7. 5.5 The Columbia University obstruction test was used to measure sexual motivation The “motivation” of the male rat is assessed in this device by the use of an electrified grid “B”.

8. Some common terms to describe aspects of male reproductive behavior: Copulatory Lock - during copulation, the penis of some male mammals (some breeds of dogs and mice are examples increases in size in a region along the shaft that it cannot be removed from the female’s vagina for a measurable amount of time. Believed to increase likelihood of paternity in species with multiple mating partners in an ovulatory period. Thursting – during copulation, the movement of the penis within the vagina. Designed to stimulate sensory nerve endings that can culminate in ejaculation in the male (and vagino-cervical orgasm in the female). Intromissions - a behavior where the male will engage in very brief insertions of his penis into the female vagina (in rats this behavior is roughly 0.25 seconds each occurance). The role for this behavior in species that have variable sized litters is to induce great number of ova to be released by the female. Ejaculation - The neuroendocrine pathway that results in the release of sperm by the male. It is a result of reaching the threshold level of stimulation of the penis resulting in the initiation of a neural circuit that triggers the release of semen from the stimulation level being reached by tissues on the penis which trigger contraction of the bulbospongiosus muscle (under the control of a spinal reflex at the level of the spinal nerves).

10. 5.7 Male copulatory patterns in mammals

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12. 5.8 Sexual behavior in the dog

13. 5.9 Sexual behavior can be restored by testosterone therapy A study in guinea pigs.