Black Rats produce a distinctive odour in their urine. This can be particularly pronounced if the population is confined to an enclosed space or is very large, and over time build urine pillars by many individuals constantly urinating in the same place.

The droppings of the black rat are on average 9mm long, thin, and described as being banana shaped. They will reuse the same runs to such an extent that depressions in the earth and paths cleared of vegetation can be clearly seen leading away from burrows.

The greasy coats of the black rat will leave a tell-tale smear on the surfaces they routinely run along which can be distinguished from other species by the broken or intermittent smears as a result of their increased agility.

The black rat is equally at home on the ground or at height, as they are adept climbers. Although usually found in trees, in the urban environment they will frequently be found in a building’s roof or attic space.

In the absence of predators or competition they will infest at ground level, but they seldom burrow unlike the Norway Rat.

The black rat serves as prey to cats and owls in domestic settings. In less urban settings, weasels, foxes, and coyotes prey upon rats. These predators have little effect on the control of the black rat population because black rats are agile and fast climbers. In addition to agility, the black rat also makes use of its keen sense of hearing to detect danger and quickly evade mammalian and avian predators. Rats serve as outstanding vectors for transmittance of diseases because they have the ability to carry bacteria and viruses in their systems. There are a number of bacterial diseases that are common to rats, and these include streptococcus pneumoniae, corynebacterium kutsheri, bacillus piliformis, pasteurella pneumotropica, and streptobacillus moniliformis, to name a few. All of these bacteria are disease-causing agents in humans.

Large-scale rat control programs have been taken to maintain a steady level of the invasive predators in order to conserve the native species in New Zealand such as kokako and mohua. Pesticides, such as pindone and sodium fluoroacetate, are commonly distributed via aerial spray by helicopter as a method of mass control on islands infested with invasive rat populations. Bait, such as brodifacoum, is also used along with coloured dyes in order to kill and identify rats for experimental and tracking purposes. Poison control methods are effective in reducing rat populations to nonthreatening sizes, but rat populations often rebound to normal size within months. Besides their highly adaptive foraging behaviour and fast reproduction, the exact mechanisms for their rebound is unclear and are still being studied.

Photos and information are provided by PelGar.