Small population size

Therefore, small populations are often considered at risk of endangerment or extinction, and are often of conservation concern.

The influence of stochastic variation in demographic (reproductive and mortality) rates is much higher for small populations than large ones.

Stochastic variation in demographic rates causes small populations to fluctuate randomly in size.

The environment can also introduce beneficial traits to a small population that promote its persistence.

[2] Immigration promotes survival by increasing genetic diversity, which will be discussed in the next section as a harmful factor in small populations.

There are two types of genetic variation that are important when dealing with small populations: Examples of genetic consequences that have happened in inbred populations are high levels of hatching failure,[16][17] bone abnormalities, low infant survivability, and decrease in birth rates.

Northern elephant seals, who also went through a population bottleneck, have had cranial bone structure changes to the lower mandibular tooth row.

The wolves on Isle Royale, a population restricted to the island in Lake Superior, have bone malformations in the vertebral column in the lumbosacral region.

Without the introduction of genetic diversity from gene flow, alleles are quickly fixed or lost.

This reduces island populations' ability to adapt to any new circumstances[19] and can result in higher levels of extinction.

[13] Human activities have been the major cause of extinctions on island in the past 50,000 years due to the introduction of exotic species, habitat loss and over-exploitation.