K-selected species, unlike r-selected species, display traits associated with living at densities close to carrying capacity and typically are strong competitors in such crowded niches, that invest more heavily in fewer offspring, each of which has a relatively high probability of surviving to adulthood. They have traits that are advantageous at high population densities. These species tend to have long lives, thrive under stable conditions, be large in size, produce few offspring, reproduce more than once in a lifetime, and provide lots of parental care to their offspring.
In stable or predictable environments, K-selection predominates as the ability to compete successfully for limited resources is crucial and populations of K-selected organisms typically are very constant in number and close to the maximum that the environment can bear (unlike r-selected populations, where population sizes can change much more rapidly).