Chapter 21 On the Tracks of Wolves and Moose

Young Gray Wolf-Romeo Every summer and a few weeks in winter, scientist investigate the Isle Royale’s pack of wolves and herd of moose Studies for almost 50 years, it is the longest- running predator prey study in the world. – Scientists would like to understand the dynamic fluctuations of the wolves and moose. – They are trying to learn about ecology

Ecology Ecology is the study of the interactions between organisms, and between organisms and their nonliving environment (land, water, etc.) – The Isle Royale is a great place to study ecology – Uninhabited by humans, protected national park, undistributed by hunting, logging, settlement – No other predators or prey on the island – Island just the right size to study ecology

Ecology Ecologists can study organisms at a number of levels: the individual, the population, the community, and the ecosystem.

Ecology At the individual level, ecologists can study how an individual organisms fares in its surroundings.

Ecology At the population level, ecologists study a group of individuals of the same species living and interacting in the same region.

Ecology At the community level, ecologists study interacting populations of different species.

Ecology At the ecosystem level, ecologists study all the living organisms in an area and the nonliving components of the environment with which they interact.

Ecology Ecology is a multidisciplinary science. It draws not only on many areas of biology but also on many other branches of science, including geography and meteorology as well as mathematics. – Living organism in an area and the nonliving components of the environment with which they interact

The study Vucetich is a population ecologist Interested in the number of wolves and moose Much of the counting is done by air. – Wolves are easy to find – Moose are solitary animals and dark colored Count a few moose and extrapolate for the entire island

Distribution patterns Moose are relatively solitary creatures – Different types of distribution patterns Random Distribution for moose – Random dispersion of individual roaming moose on the island. – The moose are hard to count for research studies. – One type of distribution pattern

Moose The distribution pattern, or the way that organisms are distributed in geographic space, depends on resources and interactions with other members of the population. – For moose, being solitary may help protect them from predation – harder to see in forest – A truly random distribution is rare in nature – Resources may be unevenly distributed, etc., – Distribution pattern are different for wolves and moose- wolves clump

Distribution patterns Distribution patterns generally reflect behavioral or ecological adaptations. Three different types:

Distribution patterns A random distribution may allow individuals to maximize their access to resources.

Distribution patterns A clumped distribution may result when resources are unevenly distributed across the landscape, or when social behavior dictates grouping.

Distribution patterns Uniform distribution usually results from territorial behavior.

Moose Few Moose swam to Isle Royale in 1900 Moose population exploded on the Isle Royale due to abundant food supply and no natural predators By 1920, more than a 1000 Rapid increase in growth rate

Population growth The growth rate of a population is the difference between the birth rate and the death rate of a given population.

Population growth Ecologists describe two general types of population growth: exponential growth and logistic growth.

Population growth Exponential growth is the unrestricted growth of a population increasing at a constant growth rate. When a population is growing exponentially, it increases by a certain fixed percentage every generation. Increase 20% each year, for example

Population growth Unrestricted growth is rarely, if ever, found unchecked in nature. As populations increase in numbers, various environmental factors such as food availability and access to habitat limit an organism’s ability to reproduce.

Population growth When population- limiting factors slow the growth rate, the result is logistic growth―a pattern of growth that starts rapidly and then slows. Disease, food limitation

Population growth Eventually, after a period of rapid growth, the size of the population may level off and stop growing. At this point, the population has reached the environment’s carrying capacity ―the maximum number of individuals that an environment can support given its space and resources.

Moose Moose arrived in 1900 By 1929 they had eaten most of the vegetation Moose exceeded the island’s carrying capacity in The population dropped due to starvation – What happened next to help the moose? – When did the wolves arrive?

Population growth Carrying capacity places an upper limit on the size of any population; No natural population can grow exponentially forever without eventually reaching a point at which resource scarcity and other factors limit population growth.

Population growth Ecologists use a variety of data to monitor the health of populations. – Moose dropping – Moose bones – Wolf scat – Urine –soaked snow

Population growth Population density is the number of organisms per given area. Wolves kill moose – As the population density of a species increases, individuals of that species may face food shortages. This is an example of a density-dependent factor―a factor whose influence on population size and growth depends on the number and crowding of individuals in the population. – Wolf predation and plant abundance have greater effect when moose population is large

Population growth Biotic refers to the living components of an environment. Not all density-dependent factors are biotic. – Food, predators, diseases Nonliving, or abiotic, factors like weather and habitat can also influence population size in a density-dependent manner.

Population growth Density-independent factors take a toll on the population no matter how large or small the population is. Most, but not all, density-independent factors are abiotic.