Rodents

Rats and mice are one of the biggest nuisance pests to man. They damage and destroy property, eat and contaminate food, and can be a vector of diseases posing concerns to human health. The following information will provide some important facts about rats and mice and hopefully help you to understand them and why the control of their populations can be of such importance.

Rats

There are two basic species of rats: Roof and Norway rats; and two basic species of mice: house and meadow. They can differ greatly from each other in many ways, especially in how they are controlled.

Roof Rats are smaller, leaner rats with a long tail that they use to balance when climbing. Their body length is usually between 6-8 inches with a tail measuring between 7-10 inches. Their average weight can be from 5-9 oz but as much as 12 oz. Their fur is soft and brown and some black intermixed, and can even be gray on top. Underneath they can be gray, white, and occasionally black. Their noses are pointed; and they have large eyes and ears (their ears are large enough to be folded over their eyes). Their droppings are ½ inch and pointed on the ends.

Norway Rats are the largest of the rats and are also known as sewer, brown or wharf rats. They are usually between 7-10 inches long and can weigh around 7-18 oz, but can grow to 20 or more oz under prime conditions. Their fur is coarse and they have a rounded or blunt nose, small eyes and ears (their ears cannot be folded over their eyes). Their droppings are long, about ¾ inch and shaped like a capsule with both ends being blunt.

Both Roof and Norway rats reach sexual maturity in 2-5 months. Roof rats have an average litter of 6-8 young and can have between 4-6 litters per year. They live for only a short time in the wild due to a variety of circumstances; their life cycle usually is around 9-12 months.

Norway rats have litters between 7-8 young per litter and they can have between 3-6 litters per year. They usually live no longer than one year in the wild.

Mice

House Mice are the most common of all rodents. They are much smaller than rats and grow between 2.5-3.5 inches long. They usually weigh between ½ -1 oz and are dusty gray on top and light gray or off white underneath. They have a pointed nose with small eyes and large ears, and their droppings are small and lack ridges. This is important because their droppings are very similar to that of the American cockroach and this is vital to identification.

Meadow Voles are mice that live in surrounding landscape. House mice can and will also live in the landscape but prefer to find their way into a structure where their superior climbing ability makes it easy for them to move around. Meadow Voles are stocky with small prominent black eyes and their ears are very small. Their tails are about as twice as long as their feet. The reason behind their small tail is that they do not use it for balance when climbing since this species prefers to burrow into the ground. They have a dense shaggy fur which can be anywhere from gray to brown on top with the underneath being gray or even a bluff color.

The house mouse is one of the highest breeding rodents as far as numbers are concerned. They reach sexual maturity in 35 days! Their pregnancies only last around 19 days and they can have up to 6 young per litter and have as many litters as 8 in a year.

Meadow voles can have about the same number of litters as a house mouse, usually 3-6, with as many young in a litter as 11. They also breed all year long but spikes in population can occur in the spring. Females reach sexual maturity in 40 days and their pregnancies last around 21 days on average. Meadow mice are the only one of the species to be somewhat active during daylight hours; while activity may be confined to the early day light hours or dusk, they are still rarely seen.

Pocket Gophers

Physical Characteristics

Pocket gophers (Thomomys spp.) are thick bodied rodents with short legs and long claws. They have long teeth that grow back into their skull and are reddish brown in color. The significance behind their name is due to the pockets or pouches in their cheeks. These pouches are on the outside and serve to hold seed picked up for feeding or storage. They range from 6-12 inches long, have small eyes and ears but a keen sense of smell.

Pocket gophers burrow underneath the surface of the ground, they use their teeth and sharp claws to dig the tunnels through sometimes extremely hard ground. Gophers can close their lips around their four large teeth that are used to not only eat but assist in digging their tunnel systems. Their tunnel systems can be from 2-4 inches in diameter usually located anywhere from 3-18 inches below the surface of the ground. These numbers can vary slightly depending upon the condition of the ground and availability of food.

Burrowing Tendencies

Gophers rarely travel above ground, they are slow animals and very easily taken by predators above the ground. Most of their visits above ground are for feeding or pushing dirt from either cleaning or expanding their tunnel system. These dirt mounds make gophers quite noticeable, they usually are located near the end of a runway and help serve in treatment of this rodent pest.

Gophers are solitary animals, they are only found together during mating or raising of young. They mate 2-3 times a year, which may also vary due to availability of food sources. They are very territorial but will take over the burrow system of another gopher if the system is vacant.

Gophers will feed on pretty much any kind of plant material; they mainly feed below the ground on the roots systems of small plants, shrubs and grass. They will though feed on the plants above the ground when the root systems or food supply become depleted. There are plants such as ivy and ice plant that are not preferred but will be fed upon if they are the only available food source.

Damage Caused by Pocket Gophers

They destroy plants not only by feeding off them, but covering them with the dirt they remove from their system. Gophers will feed off of whatever type of plant material is present at the time of infestation.

They do have preferences and that is why you will see gophers infesting turf and gazania at a much higher rate than in ground cover such as red apple. Also any type of ivy or vine plant material can provide some type of barrier to pocket gophers, but if no other food supple is near, gophers will feed off of those plants as well. Because gophers do not like to be above ground burrowing through the ground cover makes them vulnerable to predators.

They will however burrow from underneath it more readily if they can access the ground cover through already existing tunnels. These types of plants are also highly conducive to rats and mice which makes planting this type of material for repelling gophers unfavorable.

Gophers usually re-use old tunnel systems, making areas that have had activity more prone to be re-infested over time. Regular inspection and treatment programs will easily keep their populations down regardless of what type of landscape or open native areas surround a community.

Control Methods

There are several ways to control pocket gophers, ranging from trapping and baiting to the most effective way fumigation of the tunnel system. Gopher control is about knowing the rodents’ habit and proper placement of whichever method is used, traps, baits or fumigation. To treat active gophers systems each individual gopher system must be treated. Bait stations which are often used in rodent control are not used for the control of gopher’s because gophers feed below ground whereas bait stations are used to control rodents such as mice, rats an ground squirrels that feed above ground.

Trapping is an arduous process that may yield little or slow results which can be an up hill fight if the area of control is large or near open native space. This is because of the gophers’ migratory tendencies and that they re-infest old systems as well. Traps must be checked frequently and often have only caught a clump of dirt which is caused by the gophers’ pushing the dirt in front of them before pushing it out of the end of the runway.

Baiting is a more effective method and can yield very good results when placed inside the tunnel system properly. There are many types of baits but some are what is known as secondary baits. An example of this is strychnine. This bait is very effective but can also pose a threat to non-target animals, domestic or wild. Using other types of baits much as anti-coagulants will work over time but at a slower rate. Baits must be used though in cases where gophers are within 15 feet of a structure.

Fumigation is the most complete and reliable form of gopher control. It works quickly and is over 90% effective when placed properly in the burrow system. This type of control comes in the form of a tablet and is placed in the tunnel system, when it comes in contact with any type of moisture it turns into a gas. Due to recent changes in regulations this product cannot be used in the same manner as it has in the past and depending on the location and type of area treated the use of this product may not be available.

Ground Squirrels

Physical Characteristics

The California ground squirrel (Spermophilus beecheyi) is a large rodent 9-11 inches in length and has somewhat of a bushy tail. They can vary in color from gray to slightly brown and during the time they are immature may appear to have stripes or spots on their coat.

Ground Squirrels also have pouches in which they carry food and nesting material. These pouches unlike the pocket gopher are located on the inside of their mouths which actually makes the use of baits a quicker means of control.

Burrowing Tendencies

Ground squirrels are burrowing rodents and can do much damage to common areas and especially slopes. Their tunnel systems are 4-8 inches in diameter and have considerably large mounds of dirt in front of them. Ground squirrels keep their burrow systems clear and unplugged unlike the gopher. This is because they feed on seed and plants above the ground and are vulnerable to predators. Their burrows can quickly destroy a landscape, it can also damage the stability of slopes and ground areas making it dangerous to have people using these areas. They also can damage wires and sprinkler systems by chewing through them. They also damage small plants and trees by chewing bark off of them exposing these plants to the elements.

Ground squirrels also can carry many diseases, mainly due to the fleas which may be within their colonies which can range from 2-20 rodents. They can carry such diseases as tularemia and plague. Handling of dead ground squirrels is not recommended unless by a pest control technician who is aware of the problems it can cause. They quickly can populate an area in the spring when they mate and raise their young. A small seemingly harmless colony can in a brief amount of time become a hazard and a nuisance. They are active during the day and easily seen, usually from spring to fall. During the winter months squirrels will hibernate, but it is also common for young squirrels to stay active all winter long if the weather is not to severe.

Control Methods

Control of ground squirrels may vary depending on the time of year amount of activity and methods already used.

Trapping is a common method of control used for almost all rodents because it is highly successful and you an be assured the infesting rodent has been caught and removed. Because of their large populations at times and the exposure to non-target animals (wild and domestic) as well as children this is not a highly recommended method. Trapping will also take much longer and be more labor and cost intensive than the two other methods baiting and fumigating.

Baiting is a more effective method and can yield very good results when NOT placed inside the tunnel system but bait stations are used. There are many types of baits but some are what is known as secondary baits. There are many types of baits that can be used.

Some baits are placed in a bait station and allow the ground squirrels to find the bait and feed over a period of time. Other baits are broadcasted around the areas that the squirrels frequent. These types of baits come in two forms acute and chronic.

The acute baits work very quickly and can severely reduce the population in a short period of time. The draw back in using this type of bait is that the ground squirrels that get sick but do not die from it will never eat the bait again and in some cases can teach their young to stay away from it altogether.

Chronic baits are used mostly inside of a bait station because of the need for the ground squirrel to feed multiple times to receive a lethal dose. These baits come in many forms and work extremely well in seed form. They also come in pellet form but do not seem to be as accepted by the ground squirrels as the seed.

Fumigation is also an effective method in controlling ground squirrels. Solid tablets are placed inside the burrow and the system is sealed off, once the tablets come in contact with moisture they turn into a gas. This method cannot always be used due to restrictions placed on the product when used in close proximity to structures.

If you are experiencing an infestation of ground squirrels please feel free to contact us and we can come out and so a no cost inspection and provide you with some options to getting the ground squirrel population under control.