Population Numbers Population Dynamics o Short and Longterm

Population Numbers

Population Dynamics o Short- and Long-term changes in the size and age composition of populations, and the biological and environmental processes influencing those changes o Deals with the way populations are affected by birth and death rates, and by immigration and emigration, and studies topics such as aging or population declines

Population Dynamics can change due to: o Reproduction rates o Social conflicts o Movements of animals o Ecological succession or disturbance o Death

Species Welfare o Wildlife population have inherent qualities that help in defining the welfare of various species n n n Age structure Lifespan Sex ratio Natality and Mortality Migration Carrying capacity

Age Structure o Proportional amount of yound and old age classes o Age structure can be depicted by a “Triangle” n Numerous young on the bottom and very few oldsters on the told o Age may be measured in years, weeks or days depending on the species o Generally the young and very old experience the higherst mortality rates

Lifespan o Different species have different lifespans o Species towards the end of the food chain are usually much longer-lived o Combination of lifespan and age structure reveal much about the general health of a population

Sex Ratio o Each species has an “ideal” sex ratio o Appropriate sex ratios will maximize the ability of a species to produce new individuals

Natality and Mortality o Natality (birth rate) is the ability of a population to increase in numbers o Mortality relates to death rate o Reflects pressures to increase and decrease population size

Migration o Winters and dry seasons result in less available food and water o Animals will migrate to accommodate the seasonal fluctuation

Carrying Capacity o When most species approach their carrying capacity, mortality factors overtake natality and the population will decline

Factors Affecting Natality o Habitat o Minimum breeding age o Maximum breeding age o Number of young produced per year o Length of life after maximum breeding age o Sex and age composition of the population o Mating habitats related to age and sex compositions of the population

Biological Surplus o A scientific name for the number of animals in a given population that are above the carrying capacity o Most game animals have high biological surpluses o If animals are being harvested or dying faster than they can be replaced, the number of breeding animals will be reduced, and the herd or flock will not be able to sustain its numbers o Important to have enough mature animals to produce offspring, and enough offspring to replace maturing animals as they die

Biotic Potential o The maximum reproductive capacity of a population if resources are unlimited o Generally, can only be reached when environmental conditions are very favorable o A species reaching its biotic potential would exhibit exponential population growth and be determined to have a high fertility rate

Biotic Potential of a Species o Influenced by: n n n The age at which reproduction begins The time the species remain reproductive The number of offspring produced during each period of reproduction