environment activates vocalizations appropriate for a particular social
context (see Crews and Moore 1985 for a variety of hormone-behavior relations). In this section, we will review endocrine control of four major types
of vocalizations (courtship, unreceptive, aggressive, and alarm) produced by
four focus taxa: birds, frogs, rodents, and fish. A review of hormone-induced
laryngeal modifications in primates can be found in Chapter 3 by Fitch and
Hauser.
3.1. Courtship Vocalizations
3.1.1. Birds
3.1.1.1. Hormone–Behavior Relation
In most bird species in the temperate zone, courtship vocalizations are given
predominantly by males. Male songbirds (order Passeriformes) sing to
attract females (Eriksson and Wallin 1986), male budgerigars, Melopsittacus undulatus, warble during courtship (Brockway 1964), male ring doves,
Streptopelia risoria, give nest-coo vocalizations in the presence of sexually
receptive females (Lehrman 1965), and male Japanese quail, Coturnix
coturnix japonica, crow when they are visually isolated from their mates
after pair formation (Potash 1975). Females of these species, in contrast,
either vocalize much less frequently than males do, or give no courtship
vocalization at all. Instead, these females largely play the role of signal
receiver, at least in the acoustic domain.
What hormone(s) activate these courtship vocalizations? A classical
approach is to establish reliable correlations between plasma levels of
endogenous hormones and vocal production. The causal relation between
the hormone in question and the behavior is next examined by experimental manipulation of the hormones (endocrinectomy and hormone
replacement) while the behavior is observed. In most species in the
temperate zone, seasonal testicular growth elevates circulating levels of
endogenous testosterone (T) during the breeding season. Levels of plasma
T correlate very well with vocal production both in captivity and in the wild
(Marler et al. 1987, 1988; Nottebohm et al. 1987; Morton et al. 1990; Johnsen
1998). Administering exogenous T to males with low endogenous levels of
T, or to females, can induce courtship vocalization (Kern and King 1972;
Nottebohm 1980; Baptista 1987; Nowicki and Ball 1989; Nespor et al. 1996;
Romero et al. 1998). Furthermore, in many species, castrating males often
abolishes courtship vocalization, and T replacement reinstates the behavior (Pröve 1974; Arnold 1975; Adkins-Regan 1981; Harding et al. 1983,
1988). Thus, courtship vocalizations in male birds are typically activated by
elevated levels of T.
In some cases, circulating T is metabolized into different active forms
(Fig. 6.4), which then activate male vocalizations. T can be metabolized into
5-a-dihydrotestosterone (DHT) by the enzyme 5-a-reductase, or can be
aromatized into estradiol (E 2 ) by aromatases (Fig. 6.4). Androgen reduc284
A. Yamaguchi and D.B. Kelley
context (see Crews and Moore 1985 for a variety of hormone-behavior relations). In this section, we will review endocrine control of four major types
of vocalizations (courtship, unreceptive, aggressive, and alarm) produced by
four focus taxa: birds, frogs, rodents, and fish. A review of hormone-induced
laryngeal modifications in primates can be found in Chapter 3 by Fitch and
Hauser.
3.1. Courtship Vocalizations
3.1.1. Birds
3.1.1.1. Hormone–Behavior Relation
In most bird species in the temperate zone, courtship vocalizations are given
predominantly by males. Male songbirds (order Passeriformes) sing to
attract females (Eriksson and Wallin 1986), male budgerigars, Melopsittacus undulatus, warble during courtship (Brockway 1964), male ring doves,
Streptopelia risoria, give nest-coo vocalizations in the presence of sexually
receptive females (Lehrman 1965), and male Japanese quail, Coturnix
coturnix japonica, crow when they are visually isolated from their mates
after pair formation (Potash 1975). Females of these species, in contrast,
either vocalize much less frequently than males do, or give no courtship
vocalization at all. Instead, these females largely play the role of signal
receiver, at least in the acoustic domain.
What hormone(s) activate these courtship vocalizations? A classical
approach is to establish reliable correlations between plasma levels of
endogenous hormones and vocal production. The causal relation between
the hormone in question and the behavior is next examined by experimental manipulation of the hormones (endocrinectomy and hormone
replacement) while the behavior is observed. In most species in the
temperate zone, seasonal testicular growth elevates circulating levels of
endogenous testosterone (T) during the breeding season. Levels of plasma
T correlate very well with vocal production both in captivity and in the wild
(Marler et al. 1987, 1988; Nottebohm et al. 1987; Morton et al. 1990; Johnsen
1998). Administering exogenous T to males with low endogenous levels of
T, or to females, can induce courtship vocalization (Kern and King 1972;
Nottebohm 1980; Baptista 1987; Nowicki and Ball 1989; Nespor et al. 1996;
Romero et al. 1998). Furthermore, in many species, castrating males often
abolishes courtship vocalization, and T replacement reinstates the behavior (Pröve 1974; Arnold 1975; Adkins-Regan 1981; Harding et al. 1983,
1988). Thus, courtship vocalizations in male birds are typically activated by
elevated levels of T.
In some cases, circulating T is metabolized into different active forms
(Fig. 6.4), which then activate male vocalizations. T can be metabolized into
5-a-dihydrotestosterone (DHT) by the enzyme 5-a-reductase, or can be
aromatized into estradiol (E 2 ) by aromatases (Fig. 6.4). Androgen reduc284
A. Yamaguchi and D.B. Kelley