Kaitala, V., Lundberg, P., Ripa, R. & Ylikarjula, J. 1997: Red, blue and green: Dyeing population dynamics. — Ann. Zool. Fennici 34: 217–228.
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Merilä, J. 1997: Fat reserves and moult-migration overlap in goldcrests, Regulus regulus – A trade-off? — Ann. Zool. Fennici 34: 229–234.
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Wiggins, D. A. 1997: Clutch size and oviposition site characteristics of a nocturnal African silk moth Imbrasia belina (Lepidoptera: Saturniidae). — Ann. Zool. Fennici 34: 235–240.
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Otronen, M. 1997: Mating behaviour and sexual size dimorphism in Scathophaga inquinata. — Ann. Zool. Fennici 34: 241–246.
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Pasanen, S. & Karhapää, M. 1997: Can boreal common frog (Rana temporaria L.) survive in frost? — Ann. Zool. Fennici 34: 247–250.
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Soper L. R. & Payne, N. F. 1997: Relationship of introduced mink, an island race of muskrat, and marginal habitat. Ann. Zool. Fennici 34: 251–258.
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Ylönen, H., Koskela, E. & Mappes, T. 1997: Infanticide in the bank vole (Clethrionomys glareolus): occurrence and the effect of familiarity on female infanticide. — Ann. Zool. Fennici 34: 259–266.
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Hissa, R. 1997: Physiology of the European brown bear (Ursus arctos arctos). — Ann. Zool. Fennici 34: 267–287.
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Kaitala, V., Lundberg, P., Ripa, R. & Ylikarjula, J. 1997: Red, blue and green: Dyeing population dynamics. — Ann. Zool. Fennici 34: 217–228.
Numbers or densities of a natural population typically change over time. These fluctuations result from density-dependence mechanisms in the populations or external environmental variations. According to modern ecological research, time series describing population sizes and physical environments tend to be dominated by low-frequency fluctuations, whereas, contrary to this, simple population dynamic models are mostly dominated by short-term fluctuations. We review the recent theoretical advances in this ecological research theme, referred to as the ecological colour problem. Here population dynamics are analysed in the frequency domain, and named, in analogy of the light wave length, red, white or blue. We emphasise the modern tendency of deriving population ecological insight from dynamic, non-equilibrium analyses. We first deal with deterministic and stochastic single-species population dynamics. We then study how simple communities may respond to environmental noise. We finish by raising the important problem of how the colour of the environmental noise may affect the risk of population extinction.
Merilä, J. 1997: Fat reserves and moult-migration overlap in goldcrests, Regulus regulus – A trade-off? — Ann. Zool. Fennici 34: 229–234.
Moult and migration are both recognised as highly energy-demanding activities of birds. I studied moult-migration overlap in migrating goldcrests Regulus regulus to see whether birds might be trading these activities off against each other. I found that in both sexes the size of subcutaneous fat reserves were greater in birds in later stages of moult. This indicates that birds in active moult were either: (1) not able to store as much fat as birds which have completed moult, or (2) that birds in active moult used up their fat reserves quicker than birds that had completed their moult. This suggests that moult-migration overlap is costly, and there exists a trade-off between energy allocated to moult and migratory fat deposits.
Wiggins, D. A. 1997: Clutch size and oviposition site characteristics of a nocturnal African silk moth Imbrasia belina (Lepidoptera: Saturniidae). — Ann. Zool. Fennici 34: 235–240.
Oviposition site characteristics, clutch size, and hatching success were studied in a population of nocturnal silk moths (Imbrasia belina Westwood) in arid northwestern Namibia. There was little evidence of oviposition site choice based on host-tree (Colophospermum mopane) characteristics, although trees with eggs were closer to neighboring conspecific trees and small (< 1 m) trees rarely received clutches. Clutch size and hatching success were positively correlated, but neither was influenced by any of the measured tree characteristics. Similarly, neither clutch size nor hatching success was related to oviposition orientation on the leaf surface (i.e., inner or outer leaf surface). The apparent lack of host discrimination in this species may be due to a series of ecological constraints, including limited nocturnal flight periods and an unusually short adult lifespan.
Otronen, M. 1997: Mating behaviour and sexual size dimorphism in Scathophaga inquinata. — Ann. Zool. Fennici 34: 241–246.
In the dung fly, Scathophaga inquinata, females oviposit on fresh cow droppings where males arrive to mate with females before oviposition. While searching for females, single males spent most of their time in the vicinity of droppings, and were frequently involved in fights with conspecifics. On the dropping, both single males and pairs were attacked by the yellow dung fly, Scathophaga stercoraria, and hardly ever by conspecifics. Copulating males were larger than searching males, suggesting selection for large male size. Nevertheless, females were the larger sex. Only a few pairs formed at the dropping; most pairs flew to it. In copulating pairs, females were the flying individual. This was shown in an experiment where copulating pairs were tested for their ability to fly. In addition, pairs were size assortatively mated. Sexual size dimorphism in S. inquinata is discussed in relation to the mating behaviour and sexual selection on male and female size. It is suggested that loading constraints may be among the factors that maintain female-biased sexual dimorphism in this species.
Soper, L. R. & Payne, N. F. 1997: Relationship of introduced mink, an island race of muskrat, and marginal habitat. Ann. Zool. Fennici 34: 251–258.
The influence of introduced mink (Mustela vison) on an island race of muskrat (Ondatra zibethicus obscurus) was studied in insular Newfoundland using harvest statistics, habitat surveys, and food habits. More mink than muskrats are now being harvested, contrary to elsewhere in North America and predator–prey theory. Paucity of cattail (Typha spp.) in Newfoundland for building and food evidently reduces habitat quality for muskrats, probably rendering them susceptible to mink predation. Muskrats use bank burrows almost exclusively in Newfoundland. Density of muskrats is higher where they build houses with water horsetail (Equisetum fluviatile). Circumstantial evidence suggests that predation of introduced mink on a race of muskrat unadapted to mink, combined with marginal habitat conditions, probably has caused muskrat populations to decline in Newfoundland.
Ylönen, H., Koskela, E. & Mappes, T. 1997: Infanticide in the bank vole (Clethrionomys glareolus): occurrence and the effect of familiarity on female infanticide. — Ann. Zool. Fennici 34: 259–266.
We studied infanticide in the bank vole (Clethrionomys glareolus), in a species whose social organization is characterized by strict female territoriality during the breeding season. One possible origin of female territoriality could be to protect the nest site and pups from potentially infanticidal conspecifics. However, direct evidence of the occurrence of infanticide, and thus of its possible role in territorial behaviour of the bank vole females, is totally lacking. Observations in the laboratory, but also in the field and small enclosures yielded a proportion of 30% or more of infanticidal cases of both females and males intruding a strange nest. If an individual of either sex was infanticidal it killed all the pups in the nest. In 36 trials in eight 25-m2 enclosures we tested the occurrence of infanticidal behaviour in voles from three female categories: mutually familiar females with neighbouring "territories" and mutually unfamiliar "stranger" females either breeding or non-breeding. In "stranger" females the proportion of infanticidal individuals was 25% in non-breeding and 42% in breeding ones. Mutual familiarity between neighbours decreased the frequency of infanticide significantly to only 6%. In a control group of adult non-familiar males the proportion of infanticide individuals was 67%. Thus, both sexual selection (males) and resource competitions (females) infanticide was observed for the first time in the bank vole or in general in Clethrionomys spp. Territoriality in the bank vole may function to deter potentially infanticide intruders from entering the nesting area and killing pups. It might be that in a breeding system of philopatric females, mutual familiarity between neighbouring females would decrease the frequency of infanticide. This would be reflected in higher survival of young in a breeding population of philopatric females with a high degree of kinship and/or familiarity.
Hissa, R. 1997: Physiology of the European brown bear (Ursus arctos arctos). — Ann. Zool. Fennici 34: 267–287.
Although the American black (Ursus americanus) and American brown (grizzly) (Ursus arctos horribilis) bears have been the subjects of intensive physiological research, very little so far, has been done to understand the physiology of the European brown bear (Ursus arctos arctos). In our laboratory the research on the physiology of European brown bears started 10 years ago. Between 1987 and 1997, the seasonal changes in physiological indicators such as body temperature (Tb) and blood chemistry were studied in 12 bears under captive conditions in the Zoological Garden of the Department of Biology, University of Oulu, Finland. Changes in the Tb were measured either by using telemetric transmitters or dataloggers implanted into the abdominal cavity under anesthesia. The results show that the Tb decreases during the winter sleep to 3–5°C below the normal level or 37.0–37.5°C. Our bears only slept for just over three months per winter. The winter sleep started in late November/early December and ended in late February/early March. Our results do not support the theory of universal hibernation induction. Plasma from a winter-sleeping bear after injection either into Djungarian hamster (Phodopus sungorus) or laboratory rat did not affect body temperature or diurnal activity of the recipient. The urea concentration during the denning period is only half of that observed in the summer. This decrease during the denning period is in agreement with studies performed on American black and grizzly bears. In sharp contrast to earlier studies performed on the American black bear, our results reveal increases and decreases in the concentration of amino acids supporting the view that the denning bear may be even able to synthesize essential amino acids. The analysis of the total plasma fatty acids show that there may be a trend towards a greater need of unsaturated fatty acids in the denning bear as is the case of true hibernators.