Found thriving in many areas, from central Baja California, Mexico to Alaska, USA along the Pacific coast of North America, T. californicus inhabits splash pools in rocky intertidal habitat.

T. californicus is limited to pools in the upper end of the intertidal apparently by predation,[4] but it can reach quite high population densities in its habitat.

T. californicus has the ability to thrive under these variable environmental conditions (factors that limit predators such as fish to lower pools in the intertidal zone).

This copepod species has also been used as a model system in which to look at some questions in animal physiology including both neurobiology and osmoregulation.

In response to increasing or decreasing environmental salinities T. californicus changes the amount of amino acids within its cells to maintain water balance.

[18] The amino acid proline is subject to strict regulation in response to changes in salinity and this may be a common mechanism of osmoregulation across crustaceans.