|
|
Kiore (Rattus exulans) |
Ship Rat (Rattus rattus) |
Norway Rat (Rattus norvegicus) |
House Mouse (Mus musculus) |
|
Other common names |
Maori rat, Polynesian rat, Native rat, Pacific rat |
Black rat, Blue rat, Bush rat, House rat, Roof rat, Matapo |
Brown rat, Water rat, Sewer rat, Pouhawaiki |
Field mouse |
|
Adult weight (g) |
Typically 60-80; (up to 180) |
Typically 120-160; (up to 225) |
Typically 200-300; (up to 450) |
Typically 15-20; (up to 30) |
|
Max. head-and-body length ("HBL") (mm) |
180 |
225 |
250 |
115 |
|
Tail |
Slightly shorter or longer than HBL; Thin and uniformly dark all over. |
Much longer than HBL; Uniformly dark all over. |
Clearly shorter than HBL; Thick, with pale underside. |
Slightly shorter or longer than HBL; Uniformly grey-brown. |
|
Ears |
15.5-20.5 mm; Cover eyes when pulled forward; Fine hairs do not extend beyond edge of ear. |
19.0-26.0 mm; Cover eyes when pulled forward; Fine hairs do not extend beyond edge of ear. |
14.0-22.0 mm; Do not cover eyes when pulled forward; Obvious hairs extend beyond edge of ear. |
12.0-15.0 mm |
|
Adult hind-foot length |
24.5-31.0 mm |
28.0-38.0 mm |
30.0-41.5 mm |
15.0-21.0 mm |
|
Colour of upper-side of hind-foot |
Outer edge dark near ankle; Rest of foot and toes pale. |
Uniform colouring over whole foot, usually dark. |
Always completely pale. |
Uniformly grey. |
|
Fur on back |
Brown. |
Three colour variations: rattus: uniformly black; alexandrinus: brown with long black guard hairs; frugivorous: brown with long black guard hairs. |
Brown. |
Dull grey-brown. |
|
Fur on belly |
White-tipped grey giving irregular colour. |
Three colour variations: rattus: uniformly grey; alexandrinus: uniformly grey; frugivorous: uniformly white or creamy-white. |
White-tipped grey giving irregular colour. |
Uniformly grey. |
|
Length of droppings |
6.4-9.0 mm |
6.8-13.8 mm |
13.4-19.1 mm |
3.9-7.6 mm |
|
Number of nipples |
8 |
10-12 (usually 10) |
12 |
10-12 |
|
Habits |
Agile climber; Digs small holes; Nests mainly on the ground; Feeds both on the ground and in trees; Infrequent swimmer. |
Very agile and frequent climber; Rarely burrows; Nests mainly in trees and shrubs; Infrequent swimmer. |
Burrows extensively; Climbs much less frequently than the other rats; Strong swimmer; Nests underground; Very wary. |
Mainly ground dwelling, though capable climber; Nests in small holes. |
As you might notice from reading the table, it is not necessarily a straight-forward task identifying what you have caught. The information provided can be fairly variable/vague and should be taken with a grain of salt. Every source says that an identification should be made based on the weight of identifying features, as it is rare to find a specimen matching every feature perfectly.
Generally, if you put a Norway and a ship rat side-by-side, the differences are clearly evident. However, this is not always possible. Generally the clearest difference between Norway and ship rats is the size of their ears, and the length of their tails. Also, the underside of the Norway rat's tail is noticeably paler than the rest of the tail, whereas the ship rat's tail is the same colour all over. Kiore are easily confused with small ship rats, but can be identified by a small triangle of dark hair which extends onto their feet from their ankles. Ship rats' feet are completely pale, and do not have this patch. Again, weight-of-evidence should be used for any identification (for example, on Waiheke we found ship rats with surprisingly short tails).
DO NOT RELY ON PICTURES ON THE INTERNET! I am no expert, but I am strongly of the opinion that there are many misclassifications out there on the web. If you do want to see pictures, either go to a site you trust, or look up books at the library. Some references advise that if you're unsure, preserve the head or the whole body in your freezer for later identification by an expert --- if this does not worry you, that is good, but I couldn't in good conscience suggest this as a practical measure.