Polynesian rat

The Polynesian rat (Rattus exulans), also known as the kiore, is a member of the Muridae family. While it is one of the smaller rat species, its high population density and wide distribution across tropical and subtropical regions make it a significant agricultural pest that competes with humans for food resources.

This species is highly damaging to various crops, with a particular preference for sugar cane, coconut palms, pineapple, cocoa, and various oil crops. In many island agricultural systems, these rodents cause substantial economic losses by feeding on developing fruits, chewing through the stems of young plants, and consuming seeds, which hampers crop establishment.

The biology of the Polynesian rat is defined by high reproductive rates and early maturation. Breeding occurs throughout the year under favourable conditions, with females producing several litters annually. Their agility allows them to reach crops that are typically inaccessible to larger ground-dwelling rodents, making them versatile pests in orchard environments.

Damage caused by Rattus exulans is often distinct due to the precision of their gnawing. They can hollow out coconuts, gnaw through the bases of sugar cane stalks, and strip the bark of trees, exposing them to fungal infections and pests. Their presence significantly reduces the market quality of harvested products, often leading to total loss of affected fruit.

Integrated Pest Management (IPM) is essential for controlling this rodent. Recommended strategies include:

• Deployment of anticoagulant rodenticides in tamper-resistant bait stations.
• Physical exclusion using metal baffles on tree trunks to prevent climbing.
• Sanitation programs to reduce food sources and harborages near crop fields.
• Biological control through the preservation and encouragement of local avian predators.