A quest for world domination
By Lea Edgar, Librarian & Archivist, Vancouver Maritime Museum
Rats and humans have lived side by side for so long and in every corner of the globe that we assume it has always been this way. But that is not the case. Rats were once native to Asia and it was our human world-travelling ways that created the booming populations we see today. It is a fact that when we set sail for new worlds, so too did the rat.
The two main species of rats are the Norway rat and the Black rat. Both are commensal species in that they are largely dependant on humans. These rats generally live along human migration routes. It is not known when this relationship began but it could date back many thousands of years. It is likely that with the rise of agriculture, rodents were attracted to farms, as were the wild cats ready and willing to eat them. Hence, the domestication of useful felines occurred. Eventually, when water-based trading developed, rodents followed food onto ships, and cats were brought on board to dispose of them.
The Norway rat is native to Mongolia and Northern China; and the Black rat was native to the Indo-Malayan region. Black rats arrived in Europe before the Norway rat but both species eventually took up residence there. Black rats were also the first to arrive in the New World in the 16th century. Norway rats joined — and eventually displaced — their comrades by catching a ride on settlers’ ships around 1755. Norway rats tend to displace Black rats in North American climates because they are very adaptable (especially in colder climates), their diet is varied, their breeding is frequent and they are more aggressive. The Norway rat, in fact, is found on six of seven continents (they are not found in Antarctica — yet).
When a ship carrying rats docks or sinks near a previously rat-free environment, it is called a rat spill. Many islands along the coast of B.C. have been subject to this invasive species colonization. The spread of rats by ship causes numerous problems to both people and the local environment. This includes the spread of disease, destruction of property (chewing on wires, insulation, etc.), spoiling of stored food and harming or killing native species. Particularly vulnerable are ground nesting birds.
An example of a rat spill can be found on the islands of Haida Gwaii. There, bird species such as the Ancient Murrelet, have been driven away by the infestation of primarily Black rats. In 2011, Parks Canada, Haida First Nation and international partners worked to successfully eradicate rats on several islands in Haida Gwaii. The rats were first introduced to this area, as well as much of British Columbia, in the 1700s with the advent of European exploration and shipping in the region. They are known to occupy at least 18 islands throughout the archipelago. During the first phase of the project, the partner groups started systematically killing off the rats using rodenticide. They were successful in making Arichika Island rat-free. However, neighbouring islands have seen rats reappearing as they are believed to swim from the adjacent islands. Therefore, truly eradicating them from the area will be a long and difficult task. In 2013, Phase Two began. Using an aerial technique proven effective in places such as New Zealand and Mexico, a bait containing rodenticide was dispersed from the air by helicopter. Even though the rats have yet to be eliminated fully, they are already seeing an increase in native bird species and shrews. As of 2016, Murchison and Faraday Islands were declared free of Black rats. However, as of 2017, evidence of Norway rats on the island has been discovered. These rats are believed to be newcomers so the efforts are ongoing. Experts are using DNA to try to determine where the Norway rats ultimately came from.
In Prince Rupert, authorities are asking residents to collect rat parts (tails and ears) to use DNA to determine how rats came to be there. Prince Rupert was chosen because it is a main transportation route between the mainland and the rat-infested islands. Depending on the results of the DNA tests, local authorities could work with BC Ferries and shipping companies to try to stop the rats’ movements.
In 2018, Orkin Canada, a pest control company, declared Vancouver to be B.C.’s “rattiest city.” As Vancouver is Canada’s largest port, the rats there are attracted to water and the ships coming and going. As green as it may be, recycling and composting also contributes to the problem in that curb-side containers offer the rats a food source. Ports, and the ships visiting them, now actively trap and poison rats in an attempt to control the populations. A device called a rat guard is also used to try and prevent them from boarding ships on mooring lines. But these devices only appeared in the 20th century, long after the rats had effectively taken over the world. Surely, if they were used many centuries ago, we may not be facing the invasive species problem we are now in North America, and indeed globally.
Sadly, the old ship’s cat failed in preventing this global infestation. Although the damage is somewhat irreversible, small-scale efforts, such as those on the islands of Haida Gwaii, may help to give native species a chance against the rats. Areas where sensitive native species are found must be given special attention as to controlling or eliminating the rat population. With the movement of both people and goods — and therefore rats — on board ships, their elimination is unlikely. But with proper controls in place on vessels, at ports of entry and in protected natural areas, the damage this invasive world dominator can cause could be curtailed.
Lea Edgar started her position as Librarian and Archivist for the Vancouver Maritime Museum in 2013. She can be contacted at firstname.lastname@example.org.