Measured in individual numbers, they are very successful animals where they occur. In some places, they make up the dominant biomass of vertebrates. An estimated 1.88 billion individuals of the southern redback salamander inhabit just one district of Mark Twain National Forest alone, about 1,400 tons of biomass. Due to their modest size and low metabolism, they are able to feed on prey such as springtails, which are usually too small for other terrestrial vertebrates. This gives them access to a whole ecological niche with minimal competition from other groups.