The Kangaroo Rats of California: endemism and conservation of keystone species

Abstract

This review describes the great diversity and endemism of Kangaroo Rats Dipodomys spp. in California. Many species are formally listed as endangered and others are likely to be listed in the near future. We review recent efforts to conserve these small bipedal rodents. We argue that they deserve special emphasis because they have been shown to play key roles in ecosystem structure and composition. Indeed, many of the plant communities occupied by Kangaroo Rats have now been identified as at risk because of excessive habitat destruction and fragmentation. It is clear that preservation of Kangaroo Rats and their plant communities will not be achieved through simply setting aside blocks of habitat as reserves. Conservation areas will require active management in order to maintain existing biodiversity, but further studies are required to ascertain how best to manage these communities. We believe that Kangaroo Rats are important subjects for management studies and ecosystem monitoring. Preliminary studies of the size of reserves required to maintain viable populations of one species show that despite the often high abundance of Kangaroo Rats (35 animals/ha), large areas (>5 000 ha) will be required. Therefore, considerable biodiversity is likely to be protected by focusing on these species, particularly if conservation and recovery efforts are applied on a regional scale.

Contradiction in Conservation of Island Ecosystems: Plants, Introduced Herbivores and Avian Scavengers in the Canary Islands

“…Management conflicts between endangered species requiring apparently contradictory conservation strategies have been previously described (see Graham 1990 for Everglades snail kites Rostrhamus sociabilis plumbeus vs Wood storks Mycteria Americana; Goldingay et al 1997 for Giant Kangaroo rats Dipodomys ingens vs the native threatened plants, and Roemer and Wayne 2003 for San Clemente Loggerhead shrikes Lanius ludovicianus mearnsi vs San Clemente island foxes Urocyon littoralis clementae). In the case of the Canary islands and other insular systems as those described in this paper, a shallow conservation approach could recommend total prohibition of free-living goats and sheep, which would be, in turn, clearly negative for the conservation of avian scavengers of Fuerteventura, especially the highly endangered Egyptian vulture.…”

Habitat restoration opportunities, climatic niche contraction, and conservation biogeography in California's San Joaquin Desert

“…We developed habitat suitability models using 11 candidate predictor variables known or hypothesized to be important to G. sila natural history, demography, and distribution (S3 Table) , and modeled habitat suitability for a keystone taxon in G. sila habitat, kangaroo rats (Dipodomys), whose precincts and burrows generate high-quality refugia [34,35]. We obtained or derived climate, thermal physiological, and evapotranspiration data from the Basin Characterization Model (270 m resolution, mean values for 1981-2010; [36]).…”

An Invasive Grass and a Desert Adapted Rodent: is there an Effect on Locomotory Performance and is it Modified by Prior Experience or Familiarization?

“…Furthermore, rodents are among the most important primary consumers in arid ecosystems in terms of their numbers, biomass, and species diversity (Goldingay et al 1997). Consequently, they are largely responsible for supporting substantial populations of mammalian carnivores, snakes, and owls (Goldingay et al 1997). None of these generalized predators feed exclusively on rodents, let alone kangaroo rats; nevertheless, rodents are quantitatively important in their diet and a dependable prey item.…”

“…Because granivorous rodents compete not only inter-specifically, but also with other seed eaters such as birds and ants, their removal may increase the success of other competing species (Brown and Davidson 1977;Brown et al 1979). Furthermore, rodents are among the most important primary consumers in arid ecosystems in terms of their numbers, biomass, and species diversity (Goldingay et al 1997). Consequently, they are largely responsible for supporting substantial populations of mammalian carnivores, snakes, and owls (Goldingay et al 1997).…”

“…Rodents fulfill important roles in their ecosystems, as both primary consumers and abundant prey items for secondary consumers (Goldingay et al 1997;Hawkins and Nicoletto 1992;Fields et al 1999). Rodent diversity and abundance are positively correlated with plant diversity, because heterogeneous habitats provide opportunities for microhabitat segregation among rodent species (Price 1978).…”