Mice Biology Mice are the most abundant rodent in the world. There are several species of mice which are indigenous to our area but our primary concern is the house mouse, a subspecies of field mice. House mice can vary in color from brown to grey and typically have white underbellies. Adults are typically 3-4 inches in length and ½ to 1 ounce in size. Mice can be particularly destructive to our food supplies such as grain and crops because of their numbers and food preferences are similar to ours. They can also cause damage to our food supply and our homes due to contamination by their droppings and urine. Mice have pointed snouts and small round ears and their tail will have some hair on it. Mice can be distinguished from baby rats by the size and location of their ears and baby rats have hairless tails. Mouse populations can explode very quickly under the proper conditions. Mice become sexually mature and able to breed when there are about 2 months old. Babies or “pinkies” are born after about 20 days and there will often be 10-12 in each litter. Mice will breed all year long as long as there are male mice available. Mice are incontinent and will defecate constantly on many surfaces and along their travel paths. Their droppings can contain many potential risks such as Hanta Virus, toxoplasmosis, typhus, leptospirosis, etc. Special care to disinfect their droppings needs to be taken prior to removal. Mice will typically nest within 10-15 feet from their entry points and their food sources. Finding multiple locations of large amounts of droppings can indicate more than one group or family of mice, since they are highly social mammals. Nests are often built with insulation, shredded papers, scraps of cloth etc. And since mice are mammals, just like we are, they want to be inside when the weather is bad and food id hard to locate outside. Mouse activity will often spike in the fall and throughout the winter and decline in the height of summer. Treating for mice can be difficult. Inspecting for entry points larger than a dime is imperative to their control. Mice have very poor vision but powerful hearing and sense of smell. Trapping mice is highly effective if done in the right locations and with the right amount of traps. Baiting or using rodent poison can also be used if the bait is in locked stations and out of the reach of children and pets. Loose bait pellets or trays should never be used unless the area where the mice are is completely and permanently inaccessible to people and pets.
Rat Biology There are 2 important species of rats of concern in our area. The Black rat or Roof rat and the Brown rat Norway rat. Both rats are considered medium in size, weighing 9 to 12 ounces and approximately 10 inches in length with naked or scaly tails. Their coat color can range from black, brown, grey or mixes of all 3. Both rats have small ears and blunt noses. Rats can become sexually reproductive within 5 weeks of birth. Pregnancy lasts approximately 21 days and each litter can yield 7-14 babies. Black or Roof Rats prefer to nest in higher sections of building, walls voids, trees, etc. Excellent climbers. Brown rats or Norway rats prefer to nest closer to the ground or water areas. Rats in general are omnivores and considered “commensal” which means they live along side of humans and they benefit from our waste. Rats and their fleas were the primary carriers of the bubonic plague which wiped out as much as one third of the human population in all of Europe (estimated at more than 40 million people). The bubonic plague still exists today. There were 9 documented cases in the US in 2015. Rats are highly intelligent and several different methods will often be used on conjunction to solve an infestation. Openings larger than a quarter should be sealed with chew-proof materials. Bagging trash and placing inside enclosed containers is paramount to restricting their food sources. Trapping can be tricky since rats are very cautious about new objects in their home ranges but can be highly effective if done properly. Baiting can also be successful if introduced slowly and correctly.