Invasion of the Black Rat Rattus rattus Alexis Roque Karin Lisa Sirjoo

Rattus rattus Overview  The black rat is invasive and found in tropical coastal regions  Displace native species in all areas  Vector for spread of various diseases to endemic species

Research Studies  Study 1: Potential spread of introduced black rat ( Rattus rattus ) parasites to endemic deer mice ( Peromyscus maniculatus ) on the California Channel Islands. (Smith, Katherine F., Carpenter, S.M )  Study 2: Space invaders? A search for patterns underlying the coexistence of alien black rats and Galapagos rice rats. (Harris, Donna B., Gregory, S.D., Macdonald, D.W )

Deer Mice  Deer Mice are the only native mammals found on the California Channel Islands  Isolated from main land and have unique subspecies  Black rat is invasive to islands and have introduced new parasites  Lasting effects on island populations s/deermouse-250.jpg

Methods  Donation of specimens - Black rat & Deer Mice  Collected from six of the eight islands Small mammal live trapping practices Small mammal live trapping practices Euthanized, frozen, transported Euthanized, frozen, transported Sexed, aged, weighed Sexed, aged, weighed Dissected and sampled for parasites Dissected and sampled for parasites  Parasites processed by type

Collection Sites Figure 1. California Channel Islands where individuals were collected

Parasite Analysis  Inter-specific parasite transfer criteria: 1. Infects both species on islands where both co-exist 2. Does not infect deer mouse on islands where black rat is absent 3. Infects black rats in other regions GES/worms2%5b1%5d.jpg Trichuris muris faculty/dick/z346/images/syphacia3.jpg Syphacia mages/tapeworm.jpg Hymenolepis

Results  Protospirura peromysci & Trichus muris  Trichus muris met the inter-specific parasite transfer criteria  Results show that T. muris spread from black rat to deer mice  Trichus muris prevailed in deer mice where black rat was removed

Composition and Prevalence of Parasites

Study No. 1 Conclusion  Overlapping habitats and similar foraging behaviors = parasite transfer  Frequency of T. muris depends on host density  Results provide conservation implications: Parasites found in introduced species should not be ignored Parasites found in introduced species should not be ignored Parasites can remain in a population even after founder host is removed Parasites can remain in a population even after founder host is removed

Black rats and Galápagos rice rats   Galapagos islands   West of Ecuador in the Pacific Ocean   Nesoryzomys swarthi presumed extinct in 1906   Black rat introduced in the late 1600s   N. swarthi rediscovered in 1997 Fig. 1 Map of Santiago showing hair tube survey sites.

Black rats and Galápagos rice rats   SIMILARITIES   Omnivorous – eats fruits, seeds, invertebrates   DIFFERENCES   Black rat is larger; more aggressive   Nocturnal   Peak activity 2-3 hours after darkness How do they coexist?

Black rats and Galápagos rice rats   METHODS Baited hair tubes Sites along the north coast, inland, and highland Hairs extracted Species identified

Black rats and Galápagos rice rats   RESULTS 10 sites inhabited by N. swarthi Mostly thorn scrub habitat R. rattus present at all sites Fig. 2 Opuntia and Bursera thorn scrub habitat at La Bomba

Black rats and Galápagos rice rats Fig. 3 Abundance of N. swarthi and R. rattus from live trapping on four coastal (1–4) and four inland (5–8) grids at the start of the 2003 wet season (December 2002–January 2003)

Black rats and Galápagos rice rats   RESULTS Significant correlation with presence of mature cacti and rice rats Rice rats found mainly in coastal regions

Black rats and Galápagos rice rats   CONCLUSION Populations of rice rats closely correlated with Opuntia cactus density Black rats do not or can not consume cactus fruits Cactus provide a crucial resource refuge for rice rats allowing for coexistence with the black rat

Further Recommendations   Propose a study where cactus are used as main vegetation.   Follow the interactions and population numbers of rice rats versus black rats   Introduce parasite to black rats   Use arid conditions which black rats prefer as control environment   Compare rates of parasite transfer in 2 environments

References  Smith, Katherine F., Carpenter, S.M Potential spread of introduced black rat (Rattus rattus) parasites to endemic deer mice (Peromyscus maniculatus) on the California Channel Islands. Diversity distributions 12:742.  Harris, Donna B., Gregory, S.D., Macdonald, D.W Space invaders? A search for patterns underlying the coexistence of alien black rats and Galapagos rice rats. Oecologia 149: