Temporally Dynamic Reproductive Strategies and the Concept of R- and K-Selection

Breeding of the bellbird on the Poor Knights Islands, New Zealand

“…Such variation in life history characteristics indicates that the species may be able to adopt a temporally dynamic reproductive strategy, as described by Nichols et al (1976), and thus shift between relative r-and K-positions on the r-K continuum. This has important implications for the survival of bellbirds on the Poor Knights Islands should mammalian predators become established there, and indicates that in such circumstances bellbirds would tend to lay more than one large clutch each breeding season.…”

Comparative ecology of sympatric Dipodomys agilis and Dipodomys merriami populations in southern California

“…Demands for energy and water are increased by lactation in small mammals (Randolph et al, 1977;Soholt, 1978) and green vegetation in the desert-transition zone is most abundant in the spring following the winter rains. Nichols et al (1976) have proposed a life history model for desert rodents in which species employ temporal shifts between a relative r-strategy and a relative K-strategy (MacArthur & Wilson, 1967) in response to environmental fluctuations. Periods of precipitation and increased plant productivity are exploited by desert rodents through increased reproduction.…”

Patterns of recovery from low numbers in Namib Desert rodents

“…Additionally, litter sizes were larger and incidence of breeding by youngof-the ye&r higher in years of good plant production (French et al, 1974). Conley et al (1977) and Nichols et al (1976) provide discussion? 0 f the adaptive importance of these reproductive patterns.…”