Populations of ship rats (Rattus rattus) and Norway rats (R. norvegicus) were sampled over the five years 1983-87 at Pureora Forest Park, by Fenn and rat kill-traps every three months. Fenn and rat traps recorded similar capture rates in comparable habitats, although Fenns caught more heavy and fewer young rats. Ship rats (n = 1793 collected) were more abundant, heavier and larger in native forest, regardless of logging history, than in exotic forest of any age. Young ship rats (age classes 1-3) were most abundant in unlogged interior native forest, and in autumn and winter after summer and autumn breeding. Capture rates declined after peaking in 1985, probably due to reduced recruitment of young rats following lower pregnancy rates in adult females. The irregular annual seasonal cycle of reproduction and abundance observed at Pureora is the same as that described for non-commensal ship rat Z00035
The Universe makes rather an indifferent parent, I'm afraid', said Dickens' kindly Mr Jarndyce in Bleak House (Dickens 1865, p. 75). Humans have evolved to understand and intervene in the unsentimental processes of nature-with some unfortunate and unintended consequences. Back to nature or on to the future? From 1948-68, New Zealand farmers applied vast quantities of DDT to control grass grubs (not realising until the 1970s that rye grass monoculture was to blame and DDT actually made the problem worse). When the insecticide was banned in 1968, the Department of Scientific and Industrial Research (DSIR) looked at biological control using starlings. We began a study in 1970, using 500 nest boxes, and were surprised to find dead adults in the boxes. DDT killed many birds, so we asked the Ministry of Agriculture and Forestry (MAF) to check corpses-they all had DDT residues. Starlings in that area still have, after 40 years, and four times more than in any other country (Eens et al. 2013), but not at levels that would kill them. But these sudden deaths of apparently healthy birds remained a mystery until we found a pair linked together with their claws in their opponent's eyes. Normally, one bird would grip first and live to fly away. A claw into the brain via an eye socket left no mark: the perfect murder (Fig. 1). When we went to publish our observations, the editor said: 'Nature red in claw-put that in front of your title; everyone knows Darwin, even if that's all
Sixty years of work on four species of hares shows that wild populations are held by behavioural mechanisms well below the carrying capacity of their habitat. In contrast, feral populations of domesticated rabbits, and apparently all other domesticated species, expand to the food limit and starve. Some humans became domesticated (civilized) about 11,000 years ago with the advent of agriculture, lost the ‘savage’ characteristics that hold populations in check, and already are well over ecological carrying capacity. Continued growth is technologically possible at the expense of a natural environment, but renders humanity increasingly vulnerable to sudden extinction.
The advantage for camouflage of variation in colour forms (binary, multi, or continuous) is a topic of increasing interest, but there are few long-term studies. We found that the ratios of colour forms of 337 polymorphic Manuka moths (Declana floccosa), recorded at one location, did not change over 42 years. This unexpected stability, in the face of probable bird predation against commoner forms and genetic drift, might result from the moth's continuous variation that prevents predators forming a specific search image, or an unchanged food supply for the larvae. The flight period change from summer to winter, apparently the first recorded, was possibly driven by wasp (Vespula vulgaris) predation after their arrival about 1980.
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