Male mate choice and male-male competition coexist in the humpback whale (Megaptera novaeangliae)

Abstract

Male humpback whales (Megaptera novaeangliae) outnumber females on the winter grounds and compete physically for proximity to females. Analyses of identification photographs collected in Hawai'i from 1976 through 1995 and scan samples collected in 1998 showed that (i) reproductive potential (calving rate) for the following winter was greater for females without a calf than females with a calf, (ii) females without a calf were less likely to be found alone and more likely to be found in large pods than females with a calf, (iii) individual females were found in larger pods when without a calf than when with a calf, (iv) the probability of females with a calf being escorted by one or more males increased as the reproductive season progressed, and (v) head lunges occurred more commonly in all-adult pods than in pods containing a calf. We concluded that male humpback whales associate preferentially with females with high reproductive potential, that the attractiveness of individual females varies with their status (with a calf versus without a calf), that males become progressively less choosy over the course of the reproductive season as females without a calf become increasingly rare on the winter grounds, and that males expend more energy in competition over females without a calf than females with a calf.

Distribution and behaviour of humpback whale mother–calf pairs during the breeding season off Ecuador

“…It is possible that males increase mating probabilities by reducing competition with other males by moving toward shallow waters and joining a mother-calf pair (Craig et al 2002, Cerchio et al 2005. It has been stated that females with the best reproductive potential become scarce as the season progresses as, once impregnated, they leave the breeding area, and males then turn their attention to females with calves (Craig et al 2002, Cerchio et al 2005. Still, there is no evidence that the proportion of escorted female-calf pairs increased as the season progressed in Ecuador.…”

“…Dawbin 1966, Winn et al 1975, Glockner & Venus 1983, Smultea 1994, Ersts & Rosenbaum 2003, Morete et al 2007. It is unclear, however, what social and environmental conditions motivate the segregation of females and calves within the shallowest zones of their winter distribution, but it may be in response to ecological and social pressures such as predation risk (Chittleborough 1953, Herman & Antinoja 1977, harassment by males (Chittleborough 1958, Smultea 1994, Craig et al 2002, Cartwright & Sullivan 2009 and energy conservation (Whitehead & Moore 1982, Elwen & Best 2004.…”

Assessment of the level of surface activity in humpback whales during the breeding season

“…In humpback whales the social ordering seems to be transitory and characterized for fluid associations among individuals (Darling et al, 1983;Baker and Herman, 1984;Mobey and Herman, 1985;Clapham et al, 1992;Felix andHaase, 2001a, Valsecchi, 2002), in most cases limited to moments of courtship, male competence and mating, The dynamics that characterizes groups of humpback whales during the breeding season would show the "prospecting" and aggressive behavior that mature males display when looking for receptive females (Mobey and Herman, 1985). Those who invested the most would be males looking for an opportunity to mate with females having the largest reproductive potential (Tyack and Whitehead, 1983;Craig et al, 2002). The most active groups were those composed by three and four adults (A) or by adults with subadults (AS).…”

“…Other interesting aspect of the reproductive behavior of humpback whales is the production of songs. Possible functions for songs include sexual advertisement (Payne and Mc Vey, 1971;Winn and Winn, 1978;Tyack, 1981), ovulation synchronization (Baker and Herman, 1984), spacing mechanisms (Winn and Winn, 1978;Frankel et al, 1995) and social ordering (Au et al 2000;Darling and Bérubé, 2001;Craig et al, 2002). Although songs and other phonation sounds may travel further away and contain more information than percussion sounds, the later might be easily located by other whales nearby and may convey information related to local social activities that could require an immediate response.…”

Análisis espacial de los hábitats críticos del delfín nariz de botella <i>(Tursiops truncatus)</i> y la ballena jorobada <i>(Megaptera novaeangliae)</i> en el Golfo Dulce, Costa Rica: Consideraciones acerca de un proyecto de construcción de marina

“…Este comportamiento reproductivo define el uso de hábitat en esta área en particular. El uso diferencial de hábitat entre pares de hembras con crías y machos cantando en cortejo se disipa por lo reducido de la escala geográfica donde ocurren estos eventos y por la relación implícita entre la disponibilidad de hembras y la mayor proporción de machos en áreas de agregación invernal (Craig et al 2002;Clapham, 2008), lo que a su vez genera la presencia de grupos competitivos de machos persiguiendo hembras (Craig et al 2002;Spitz et al 2002), incluso aquellas con crías de la temporada (Clapham, 2000).…”