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Research Highlights
Elephant Seals: Mating and Reproductive Success
The mating system of elephant seals is described from tracking marked males and copulations (Le Boeuf and Peterson 1969; Le Boeuf 1974). Males compete for social rank in a dominance hierarchy that confers access to females and mating. The alpha male and a few other top-ranking males monopolize mating.
The lifetime reproductive success of male and female elephant seals is determined from tracking the animals throughout their lives (Le Boeuf 1974; Le Boeuf and Reiter 1988; Le Boeuf, Condit and Reiter 2019). Most males and females (75%) do not live to reproductive age. A few males of the most successful males may inseminate 120 to 200 females in life but most mate with few or no females. Most surviving females produce only 2 to 4 pups in life before they die, but a few females produce up to 20 pups in life.
The female elephant seal exerts choice over mates (Cox and Le Bœuf 1977). They reject all mating attempts by bellowing loudly. This announces that mating is imminent, which causes all males in the vicinity to chase off the mounting male if he is lower rank. The upshot is that the only male that can attempt to mate without being interrupted is the alpha male. The female acquiesces and mates with this male of demonstrated fitness that is the most fitting sire for her pup and for her reproductive success.
Elephant Seals: Diving and Foraging
The mating system of elephant seals is described from tracking marked males and copulations (Le Boeuf and Peterson 1969; Le Boeuf 1974). Males compete for social rank in a dominance hierarchy that confers access to females and mating. The alpha male and a few other top-ranking males monopolize mating.
The lifetime reproductive success of male and female elephant seals is determined from tracking the animals throughout their lives (Le Boeuf 1974; Le Boeuf and Reiter 1988; Le Boeuf, Condit and Reiter 2019). Most males and females (75%) do not live to reproductive age. A few males of the most successful males may inseminate 120 to 200 females in life but most mate with few or no females. Most surviving females produce only 2 to 4 pups in life before they die, but a few females produce up to 20 pups in life.
The female elephant seal exerts choice over mates (Cox and Le Bœuf 1977). They reject all mating attempts by bellowing loudly. This announces that mating is imminent, which causes all males in the vicinity to chase off the mounting male if he is lower rank. The upshot is that the only male that can attempt to mate without being interrupted is the alpha male. The female acquiesces and mates with this male of demonstrated fitness that is the most fitting sire for her pup and for her reproductive success.
Sea Lions: Mating
Southern sea lion males breeding in Patagonia, Argentina, face a dilemma (Campagna, Le Boeuf and Cappozzo, 1988). They attempt to corral a half dozen or so females near them for mating. However, males on the periphery, that are kept out of the breeding area, stage group raids where they attempt to steal females and hoard them in or out of the breeding area. During a raid, the male with females must vacillate between fending off the raiders and not letting his female escape. Havoc ensues. Males cope as best as they can. Females have the opportunity to associate with a different male. The raiders rarely make off with a female and some steal a pup and treat as if it were a female.
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