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Rat Species
There are two main types of rats that cause concern in Thailand. The Brown Rat (common rat) and the Black Rat (sewer rat) are commonly found in both private homes and business property.
Black Rat
(Rattus rattus)
Black rats can be found in coastal towns and in many urban environments across Thailand.
Appearance
- The black rat is between 16–24cm in length, with a tail longer than the head and body.
- It grows to between 150–200g in weight.
- They have a pointed nose, large ears and a slender body.
Lifecycle
- Black rats produce 5–10 young per litter, and have between 3–6 litters a year.
- The gestation period is about 3 weeks.
- It only takes between 12–16 weeks from birth for them to reach sexual maturity.
Habits
- They are incredibly agile and very good climbers.
- Their preferred food is moist fruits. Black Rats will eat around 15g of food a day and drink 15ml.
Brown Rat
(Rattus norvegicus)
Brown rats usually prefer ground living and burrowing, but sometimes they can be known to climb.
Appearance
- The brown rat is up to 40 cm in length, with a tail shorter than the head and body.
- It grows up to between 350–500g in weight.
- It has a blunt nose, small ears and a thicker body when compared to the Black Rat (Rattus rattus).
Lifecycle
- Rats have 7–8 young per litter, and between 3–6 litters a year.
- The gestation period is about 3 weeks.
- It only takes 10–12 weeks from birth to reach sexual maturity.
Habits
- Preferred food is cereals, although they are omnivorous.
- They will eat around 30g of food a day and drink 60ml.
House Mouse
(Mus domesticus)
House mice are active all year round, which means you could find them invading your home or business at any time.
Appearance
- Size: 70 – 95mm in length, with a tail around the same length.
- Weight: 12 – 30g.
- Their relatively small feet & head and large eyes & ears distinguish them from a young brown rat (Rattus norvegicus).
Lifecycle
- 4 – 16 young per litter; 7 – 8 litters a year.
- Gestation period of about 3 weeks.
- 8 – 12 weeks from birth to sexual maturity.
Habits
- Usually ground living and burrowing, but often climbs.
- Preferred food is cereals.
- Will eat around 3g of food a day and can survive without any additional water. They will drink up to 3ml a day if their diet is particularly dry.
Field Mouse
(Apodemus sylvaticus)
Field mice rarely venture into inhabited buildings but in the winter months, they will go into outhouses and sheds where fruit and vegetables are stored.
Field mice are a big threat to businesses operating in farming and agriculture.
Appearance
- Size: adult head and body 80 – 100mm in length; Tail 70 – 90mm.
- Weight: Male can weigh 25g, and the female 20g.
- Sandy / orange brown fur on the head and back.
- Yellowish fur on the flanks and white on the belly.
- There is usually a small streak of yellow on the chest.
Lifecycle
- Their lifespan averages two to three months, but they can survive as much as 20 months in the wild, or two or more years in captivity.
- Breeding seasons are March/April to October/November and gestation lasts approximately 25 days. They grow their first fur after six days; their eyes open after 16; and they are weaned at around 18 days old.
- Survival of the young and adults is poor during the first half of the breeding season as adult males can be aggressive towards one another and to the young, who are then driven from the nest.
Habits
- They eat a high proportion of the seed crop of trees such as oak, beech, ash, lime, hawthorn and sycamore. In Thailand, numbers can reach plague proportions in the grain belt areas.
- Small snails and insects are particularly important sources of food in late spring and early summer when seeds are less available.
- They also eat apples and will attack newly planted legume seeds.
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