The influence of fire on rodent abundance at the N'washitshumbe enclosure site, Kruger National Park, South Africa

The relative population numbers of rodents were studied in nine habitats in and outside the N’washitshumbe enclosure site, Kruger National Park, before and after burning the firebreaks that surround the enclosure. Trap success was exceptionally high, and the field work is suspected to have coincided with a Mastomys population explosion. This genus dominated the small mammal communities before and after the burn, and never disappeared from the burnt patches. Its numbers also did not crash directly after the burn, as have been reported in most other studies. Movement from the burnt areas was observed, which may have had a significant impact on the numbers of rodents caught both inside the enclosure and in the more natural areas outside. Our study suggests that fire can be investigated as a tool to keep rodent densities down in areas where they are nuisance animals, especially when used in conjunction with models that forecast outbreaks of Mastomys. It also emphasizes the value of long-term studies informing management strategies for animal damage control and biodiversity and ecosystem conservation.http://www.bioone.org/loi/afzoab201

The microenvironment of house mice on Marion Island (sub-Antarctic)

On Marion Island, house mice (Mus musculus) establish burrow systems that range from unbranched corridors 0.5 m long with a single chamber (in some instances without a chamber) to complexly branched systems extending over an area of up to 4 m2 and containing up to four chambers. Total underground area occupied by burrow systems (chambers plus corridors) was from 5 to 23 m2 ha-1, corresponding to burrow-system volumes of 250-1,300 dm3 ha-1. In autumn, about three-quarters of chambers contained small food caches. Most (87%) entrances to burrow systems faced away from prevailing winds, especially winds that bring snow, hail or rain. Seasonal and diurnal temperature variations in burrows are considerably dampened (daily minimum in burrows seldom drops below 2°C), compared with the air just above the vegetation canopy. Over the whole year, total night-time warmth in a burrow (heat sum, 24,883 degree hours) was 53% greater than at the top of the canopy (16,317 degree hours). Burrows' entrances are generally connected above ground by runways (paths and tunnels through the vegetation). Runways also represent a warmer environment than the air above the canopy during the breeding season at night (13,466 degree hours at the runway surface compared with 11,900 degree hours at the top of the canopy). House mice, which are living close to their physiological limits, temperature-wise, on Marion Island thus evade the worst extremes of the island's climate by constructing burrows and above-ground runways and this is an important factor in their survival.Articl

Seasonal changes in age class structure and reproductive status of house mice on Marion Island (sub-Antarctic)

Feral house mice on sub-Antarctic Marion Island become reproductively active (males scrotal, females with perforate vaginas or pregnant) at an age > 60 days and breed until death, which may occur at more than 13 months. Breeding is strongly seasonal; pregnant or lactating females were found only from October to May. A substantial proportion of mice old enough to breed in one summer overwinters to form a significant component of the breeding population the following summer but it is unlikely that any survive a second winter. The onset of breeding is closely synchronized with increasing day length but occurs about 2 months before mean temperature at the ground surface starts to increase significantly. Cessation of breeding is more closely associated with declining temperatures in late summer. For both males and females, the best correlation between reproductive activity and any of the temperature parameters measured was with average maximum temperature 1 cm above the ground. Competition for macroinvertebrate prey increases sharply in early winter due to high mouse numbers. The breeding season in 1991/1992 and 1992/ 1993 was at least 2 months longer than in 1979/1980, because the mice started breeding earlier, and stopped breeding later, in 1991/1993. The later cessation of breeding in 1991/1993 was despite the fact that there was a greater competition for macroinvertebrate prey, and that mean air temperatures during the early winter months were lower, than in 1979/1980.Articl

Prey use by four syntopic carnivores in a strandveld ecosystem

The diet of four syntopic carnivore species (caracal Felis caracal, water mongoose Atilax paludinosus, small grey mongoose Galerella pulverulenta, and yellow mongoose Cynictis penicillata) over a 12-month period in a coastal shrub ecosystem was examined using scat analysis. Use of prey by all four species fluctuated synchronously and tracked corresponding fluctuations in prey availability. This, as well as the use of relatively small food items (e.g. beetles, scorpions and spiders), indicate an absence of dietary specialization and an opportunistic feeding behaviour in the carnivores studied. Food niche breadth in all four species changed seasonally, being widest during spring and contracting gradually towards winter. A considerable degree of food niche overlap existed between species. Rodents (mainly Rhabdomys pumilio and Otomys unisulcatus) were the main prey items of all four carnivore species and were used heavily throughout the year, despite marked declines in numbers towards winter.Articl

Comparison of the diet of the yellow mongoose in a coastal and a Karoo area

The diets of Cynictis penicillata occurring in Karoo and West Coast Strandveld ecosystems were compared, using faecal analysis. Insects were the most important prey in both study areas. Rodents and reptiles were important as food at the coast, while bird remains were present in >10% of scats from both areas. Only at the coastal site did dietary patterns of yellow mongooses reflect fluctuations in prey availability. The presence, in small quantities, of other prey types in scats at both study sites indicates opportunistic feeding behaviour. -from Author

Home-range use, activity, and density of caracal in relation to prey density

Two male and three female caracal Felis caracal were radio-tracked over a 1-year period in arid shrub on the west coast of South Africa, by day and night over at least 130 days for each caracal, and uninterrupted for up to 120 h at a time. These results, on short-term use of space, were related to concurrent availability of prey. The use by caracal of specific plant communities showed a significant positive correlation to prey biomass of rodents. Males had much larger home-ranges (26.9 ± 0.75 km2) than females (7.39 ± 1.68 km2). Male home-ranges overlapped completely with those of females, whereas female ranges overlapped between 0 and 19%. Caracal were active by night and day; onset of activity was affected more by ambient temperature (T(A)) than photoperiod. Caracal were active significantly longer on nights colder than 20°C. Females ceased activity at T(A) > 20°C, males at T(A) > 22°C. Males foraged faster than females (667 vs. 312m h-1) and moved more than twice the distance of females during an active period. Calculated density of caracal was between 0.23 and 0.47 km-2.Articl

The diet and impact of house mice on a sub-Antarctic island

An analysis of the stomach contents of house mice (Mus musculus L.) at three sites on Marion Island (47°S, 38°E) over a 1-year period showed that the mice feed mostly on terrestrial macroinvertebrates but that plants (mainly seed) are an important component of the diet in mid- to late summer. Larvae of a flightless moth, weevil larvae and adults and, at one of the sites, earthworms were the invertebrate items that showed the highest importance value over the year. Diet diversity was slightly lower in summer and autumn than in winter and spring. Diet variety was lowest in midsummer and highest in either autumn or winter, depending on the site. Mean stomach-content mass was significantly higher in midwinter than during the rest of the year. When offered prey of different types and sizes, mice selected moth larvae first in 92% of the trials; earthworms or weevil adults were most frequently selected second, and weevil larvae fourth. An introduced slug species was selected only once, as the last choice and only part of it was eaten. With both moth larvae and earthworms, the heaviest individual offered was almost always chosen first. Surprisingly, mice never consumed more than about half of the seed offered to them and their condition deteriorated severely during the trials with seed; in a third of the trials with two types of seed, the mice completely ignored the seed. The impact of mice predation on invertebrates was assessed at two of the sites - a dry mire and a coastal biotic herbfield that is influenced by seabird and seal manuring. Moth larvae and adults, weevil larvae and adults, earthworms, spiders and flies made up > 90% of the animal remains in the stomach contents over the year and, on average, the mice daily consumed 45 g (dry mass) ha-1 of those invertebrates at the mire and 194 g ha-1 at the biotic site. Moth larvae made up a substantial proportion of these amounts; average daily consumption was 30 g ha-1 at the mire and 107 g ha-1 at the biotic site. In terms of the amount consumed in relation to biomass, the heaviest impact of mice at both sites was on weevil adults; at the biotic site mice daily consumed 13% of weevil adult biomass in autumn and nearly 6 times the annual average biomass over the year. At the mire, slightly more than the annual average weevil adult biomass was consumed over the year. The consumption of invertebrates by mice found in this study (1992/1993) was about 20% greater than in 1979/1980. The most striking changes in annual average consumption rate between 1979/1980 and 1992/1993 were for weevil larvae (increased nearly fourfold) and earthworms (increased sixfold at the biotic site and threefold at the mire). In contrast, the consumption of spiders at both sites decreased between 1979/1980 and 1992/1993.Articl

The influence of fire on rodent abundance at the N’washitshumbe enclosure site, Kruger National Park, South Africa†

The relative population numbers of rodents were studied in nine habitats in and outside the N’washitshumbe enclosure site, Kruger National Park, before and after burning the firebreaks that surround the enclosure. Trap success was exceptionally high, and the field work is suspected to have coincided with a Mastomys population explosion. This genus dominated the small mammal communities before and after the burn, and never disappeared from the burnt patches. Its numbers also did not crash directly after the burn, as have been reported in most other studies. Movement from the burnt areas was observed, which may have had a significant impact on the numbers of rodents caught both inside the enclosure and in the more natural areas outside. Our study suggests that fire can be investigated as a tool to keep rodent densities down in areas where they are nuisance animals, especially when used in conjunction with models that forecast outbreaks of Mastomys. It also emphasizes the value of long-term studies informing management strategies for animal damage control and biodiversity and ecosystem conservation.Key words: small mammal communities, fire, Mastomys, indicator species, animal damage control, biodiversity, ecosystem conservation