Invasion of the Black RatInvasion of the Black RatRattus rattusRattus rattus

Alexis RoqueAlexis Roque

Karin Lisa SirjooKarin Lisa Sirjoo

Rattus rattusRattus rattus Overview Overview

The black rat is invasive and found in The black rat is invasive and found in tropical coastal regionstropical coastal regions

Displace native species in all areasDisplace native species in all areas Vector for spread of various diseases to Vector for spread of various diseases to

endemic speciesendemic species

Research StudiesResearch Studies

Study 1: Potential spread of introduced black rat Study 1: Potential spread of introduced black rat ( Rattus rattus ) parasites to endemic deer mice ( Rattus rattus ) parasites to endemic deer mice ( Peromyscus maniculatus ) on the California ( Peromyscus maniculatus ) on the California Channel Islands. (Smith, Katherine F., Channel Islands. (Smith, Katherine F., Carpenter, S.M. 2006.) Carpenter, S.M. 2006.)

Study 2: Space invaders? A search for patterns Study 2: Space invaders? A search for patterns underlying the coexistence of alien black rats underlying the coexistence of alien black rats and Galapagos rice rats. (Harris, Donna B., and Galapagos rice rats. (Harris, Donna B., Gregory, S.D., Macdonald, D.W. 2006.)Gregory, S.D., Macdonald, D.W. 2006.)

Deer Mice Deer Mice Deer Mice are the only Deer Mice are the only

native mammals found on native mammals found on the California Channel the California Channel IslandsIslands

Isolated from main land Isolated from main land and have unique and have unique subspeciessubspecies

Black rat is invasive to Black rat is invasive to islands and have islands and have introduced new parasitesintroduced new parasites

Lasting effects on island Lasting effects on island populationspopulations

http://www.sdnhm.org/fieldguide/mammals/images/deermouse-250.jpg

MethodsMethods

Donation of specimens - Black rat & Deer Donation of specimens - Black rat & Deer Mice Mice

Collected from six of the eight islands 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 parasitesDissected and sampled for parasites

Parasites processed by type Parasites processed by type

Collection SitesCollection Sites

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

Parasite AnalysisParasite Analysis Inter-specific parasite transfer criteria:Inter-specific parasite transfer criteria:

1.1. Infects both species on islands where both Infects both species on islands where both co-exist co-exist

2.2. Does not infect deer mouse on islands Does not infect deer mouse on islands where black rat is absentwhere black rat is absent

3.3. Infects black rats in other regions Infects black rats in other regions

http://www.nematode.net/IMAGES/worms2%5b1%5d.jpg

Trichuris murisTrichuris muris

http://www.umanitoba.ca/science/zoology/faculty/dick/z346/images/syphacia3.jpg

SyphaciaSyphacia

http://www.4optimallife.com/Images/tapeworm.jpg

Hymenolepis Hymenolepis

ResultsResults

Protospirura Protospirura peromysci peromysci & & Trichus Trichus muris muris

Trichus muris Trichus muris met the met the inter-specific parasite inter-specific parasite transfer criteriatransfer criteria

Results show that Results show that T. T. murismuris spread from spread from black rat to deer miceblack rat to deer mice

Trichus muris Trichus muris prevailed in deer mice prevailed in deer mice where black rat was where black rat was removedremoved

http://wotan.cse.sc.edu/perobase/images/p_manicu.jpg

Composition and Prevalence Composition and Prevalence of Parasites of Parasites

Study No. 1 ConclusionStudy No. 1 Conclusion

Overlapping habitats and similar foraging Overlapping habitats and similar foraging behaviors = parasite transfer behaviors = parasite transfer

Frequency of Frequency of T. murisT. muris depends on host depends on host density density

Results provide conservation implications:Results provide conservation implications: Parasites found in introduced species should Parasites found in introduced species should

not be ignorednot be ignored Parasites can remain in a population even Parasites can remain in a population even

after founder host is removedafter 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 trappingon four coastal (1–4) and four inland (5–8) grids at thestart 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 References

Smith, Katherine F., Carpenter, S.M. 2006. Potential spread of Smith, Katherine F., Carpenter, S.M. 2006. Potential spread of introduced black rat (introduced black rat (Rattus rattusRattus rattus) parasites to endemic deer ) parasites to endemic deer mice (mice (PeromyscusPeromyscus maniculatusmaniculatus) on the California Channel ) on the California Channel Islands. Diversity distributions Islands. Diversity distributions 1212:742.:742.

Harris, Donna B., Gregory, S.D., Macdonald, D.W. 2006. Harris, Donna B., Gregory, S.D., Macdonald, D.W. 2006. Space invaders? A search for patterns underlying the Space invaders? A search for patterns underlying the coexistence of alien black rats and Galapagos rice rats. coexistence of alien black rats and Galapagos rice rats. Oecologia Oecologia 149149:276-288.:276-288.