HORMONES AND MATING BEHAVIOR 



1175 



been favored subjects for investigation, 

 that much of the thread of thought which 

 follows was developed during investigations 

 of these species, and that for problems of 

 concern to the endocrinologist this work 

 still is the richest source of information. At 

 the same time, we do not belittle the fact 

 that much has been learned from observa- 

 tions and experiments on other lower mam- 

 mals, submammalian vertebrates, infrahu- 

 man primates, and man. Important concepts 

 not appreciated at the time were developed 

 from early and relatively isolated studies of 

 the ringdove (Craig, 1914, 1918) and chicken 

 (Goodale, 1918). Latterly, careful observa- 

 tions by ethologists and zoologists have pro- 

 vided the substance for a comparative con- 

 sideration of many problems. Some of the 

 descriptions, notably that of the male guppy 

 (Baerends, Brouwer and Waterbolk, 1955), 

 are more refined than any given of a mam- 

 mal and all are of value for the breadth they 

 add to what otherwise would have been a 

 laboratory study in the narrower sense. 



II. Mating Behavior 



A. THE MALE 



The behavior varies from species to 

 species, but in many species and particu- 

 larly in mammals genital examination, if 

 not copulation with ejaculation, is usually 

 immediate when individuals of opposite 

 sexes are placed together (Hamilton, 1914; 

 Stone, 1922; Bingham, 1928; Yerkes and 

 Elder, 1936; Young and Grunt, 1951; Lars- 

 son, 1956). In such a situation the interval 

 between the beginning of a test and the first 

 display of interest in the establishment of 

 sexual relations may be taken as a measure 

 of the strength of sexual behavior (Soulairac 

 and Coppin-Monthillaud, 1951). The subse- 

 quent behavior is composed of several ele- 

 ments. The number distinguished depends 

 somewhat on the investigator, but also on ex- 

 perience. In general when a species has been 

 used extensively as have the rat and guinea 

 pig the later articles should be consulted 

 (Stone, Tomilin and Barker, 1935; Stone 

 and Ferguson, 1940; Beach, 1944b; Beach 

 and Holz, 1946; Soulairac and Coppin- 

 ISIonthillaud, 1951 ; Young and Grunt, 1951 ; 

 Larsson, 1956). 



When a female rat is placed in a cage 



with a cage-adapted male the latter usually 

 begins to copulate immediately. Often, 

 however, he begins in a few seconds to ex- 

 amine her anogenital region. Another pre- 

 copulatory act is a nibbling at the head or 

 body. The copulatory act is described as 

 coming with such a definiteness and orderly 

 sequence of elements that it can easily be 

 distinguished from precopulatory behavior 

 (Stone, 1922) . The male mounts the female 

 from the rear and clasps his forelegs about 

 her laterolumbar region in what Beach 

 (1944b) calls a clasp-without-palpation. 

 While clasping the female, the male pal- 

 pates her sides with rapid movements of his 

 forelimbs and simultaneously his pelvic 

 region is moved in rapid, piston-like thrusts 

 (palpation-with-pelvic-thrusts). He then 

 slips off the female's back rather weakly. 

 In nearly every instance this termination 

 of contact with the female indicates a fail- 

 ure to achieve intromission; behavior of 

 this type is designated an incomplete copu- 

 lation or attempt. With what Beach desig- 

 nates copulation or complete copulation, the 

 palpation-with-pelvic-thrusts occurs, but a 

 new element is added. After a final and un- 

 usually forceful thrust, the male lunges 

 backward and often throws himself several 

 inches from the female. This backward 

 lunge nearly always is indicative of intro- 

 mission. Stone and Ferguson (1940) esti- 

 mated from a cinematographic study that 

 the duration of these intromissions is Vs to 

 2/3 of a second and that during each intro- 

 mission 2 and 9 pelvic thrusts occur. When 

 intromission is terminated by ejaculation 

 the backward lunge is omitted. Instead the 

 male continues to press against the female, 

 thus prolonging intromission, and then, re- 

 leasing his clasp, slowly raises his forelegs 

 as the ejaculate is emitted and the penis 

 withdrawn. In most tests ejaculation is not 

 seen during the first intromission, but it 

 has been observed at this time in tests in- 

 volving observations of sexual behavior 

 over a period of hours (Beach, 1956). Us- 

 ually, however, from 3 to 44 intromissions 

 precede ejaculation. A spell of recovery, the 

 refractory period, is then required, during 

 which the male is uninfluenced by any sex- 

 ual stimuli (Larsson, 1956). Satiation is not 

 reached until there have been 3 to 10 ejacu- 



