It is impossible to underestimate the damage wrought to mankind and to any number of local environments by the black rat. For starters, it was the black rat that carried the Oriental rat flea (Xenopsylla cheopsis), which in turn carried the bubonic plague. Ravaging Europe from 1347 through 1352, the so-called Black Death killed an estimated 25 million people. As if that weren't enough, the black rat is also a carrier of lassa fever, murine typhus, ratbite fever, and leptospirosis.
The black rat also destroys vast amounts of food supplies through contamination and is responsible for the extinction of thousands of species worldwide. The black rat originally came from India and has spread to every continent except Antarctica. Beginning about 20,000 years ago, possibly related to human migrations, the black rat spread to the Middle East, then eventually into Europe. It reached the other continents during the Age of Exploration (3200 BC-1779 AD). Its nickname "ship rat" aptly describes the black rat's success as a stowaway; the early explorers unwittingly brought this adaptable rodent to nearly every one of their destinations. Once established, the black rat would wreak havoc on the native ground-dwelling birds, small mammals, reptiles, snakes, and insects.
The black rat, the Norwegian rat, and the house mouse, in large part thanks to their close relationships to humans, must now be considered the most successful mammals on earth, vastly outnumbering the 6.7 billion people on this planet.
The black rat tends to be nocturnal, so the best chance to see one is in the evening, particularly around dumpsters or back alleys. During the day the black rat often nests in palm trees.
In many areas the poisons used to try to control the black and Norwegian rats can sometimes be responsible for the death of owls, hawks, bobcats, and other creatures. For a healthy predator, a poisoned rat is an easy target. When it kills and eats the rat, it consumes a small amount of the same poison the rat has ingested. Even if the predator survives the initial poisoning, repeated consumption of poisoned rodents will eventually kill the animal. The use of any animal poisons in controlling varmints such as rats and squirrels is strongly discouraged. Instead, try electric (a.k.a. the rat "zapper"), glue stick or mechanical traps, available at most hardware stores.
The black rat is preyed upon by all major predators. It lives a little more than a year in the wild. There is a relationship between black rat populations and raccoons. Raccoons feed heavily on black rats, which often nest in cabbage palms. When the local raccoon populations are decimated by canine distemper or other pathogens, the black and brown rat populations explode, causing a massive pest problem in homes and condominiums in the surrounding region.
In the Know:
Black Rat (Rattus rattus)
Other names: ship rat, roof rat, palm rat, house rat, Alexandrine rat, Old English rat
Status: FL=thriving, IUCN=LC
Length: with tail, 13.6-18 in. (34-45 cm)
Weight: 2.5-10.5 oz (70-300 g)
Reproduces: breeds year round and can have up to six litters a year with 10 offspring per litter
Found: All Counties, coastal, near coast, mainland
Months found: JFMAMJJASOND (note: black rats breed all year round).
This article is an excerpt from Living Sanibel-A Nature Guide to Sanibel & Captiva Islands by Charles Sobczak. The book is available at all the Island bookstores, Baileys, Jerry's and your favorite online sites.