. Animal Ecology. Animal ecology. lively with tendencies toward ptiiyaiidry (Kendeigh and Baldwin 1937). Mating behavior is therefore to some extent adaptable in order to compensate for lop- sided sex ratios and to maintain high reproductive capacity. BREEDING AGE The age at which young animals first at- tain the ability for reproduction affects the reproduc- tive capacity and rate of growth of populations. Planktonic entomostracans are sexually mature in a few days ; insects, often in a few weeks. Among birds, a tropical sparrow is known to reach full reproductive level in six to eight months
. Animal Ecology. Animal ecology. lively with tendencies toward ptiiyaiidry (Kendeigh and Baldwin 1937). Mating behavior is therefore to some extent adaptable in order to compensate for lop- sided sex ratios and to maintain high reproductive capacity. BREEDING AGE The age at which young animals first at- tain the ability for reproduction affects the reproduc- tive capacity and rate of growth of populations. Planktonic entomostracans are sexually mature in a few days ; insects, often in a few weeks. Among birds, a tropical sparrow is known to reach full reproductive level in six to eight months (Miller 1959). Small non-tropical song birds commonly nest during spring and summer of the year following that in which they hatched, but banding of nestling house wrens indi- cated that 12 to 18 per cent failed to do so until the second or third year (Kendeigh and Baldwin 1937). Upland game birds probably nest as yearlings; geese and wild turkeys do not nest until they are two years old; common terns, commonly only after three years. Some lizards and snakes require two to three years to reach sexual maturity: turtles much longer. Females of the voles may mate at 13 days, even before they are weaned, and give birth to their first litter when only 33 days old (Frank 1957). Woodland white-footed mice born in spring may pro- duce young late in summer; but most small and me- dium-sized mammals do not breed until one year old. Beaver, wolf, lion, and whale breed when two years old. Big game mammals, such as deer, bison, and bear, reach maturity only after three years. The elephant is said to require 8-16 years, and the rhi- noceros 20 years (Spector 1956: 115, 119). NON-BREEDING POPULATIONS Although the breeding population of a par- ticular mammal, bird, or other animal is the only fraction of the total population of a species concerned with its reproductivity, there is often present in an area a substantial, though inconspicuous, non-breed- ing population that must be co
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Keywords: ., bookcentury1900, bookcollectionbiodive, booksubjectanimalecology
