Habitat fragmentation and predation: Experiments with bank voles (Myodes glareolus) and least weasel (Mustela nivalis nivalis)

Date:
2018/06/14

Time:
10:00

Room:
K306 Anton

Habitat fragmentation and predation: Experiments with bank voles (Myodes glareolus) and least weasel (Mustela nivalis nivalis)

(Oral and Poster)

Marko Haapakoski
marko.j.haapakoski@jyu.fi

Department of Biological and Environmental Science, Konnevesi Research Station, University of Jyväskylä, PO Box 35, 40014 Jyväskylä, Finland, Finland
,
Janne Sundell
Lammi Biological Station, University of Helsinki, Pääjärventie 320, 16900 Lammi, Finland
,
Hannu Ylönen
Department of Biological and Environmental Science, Konnevesi Research Station, University of Jyväskylä, PO Box 35, 40014 Jyväskylä, Finland, Finland

DOI: 10.17011/conference/eccb2018/107106

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Habitat loss and fragmentation are the main causes for innumerable population declines and species having become threatened or extinct. Habitat fragmentation inevitably affects behaviour and social interactions of individuals. These are likely to form an essential part of the mechanism behind observed population declines. Predator - prey interaction is strong factor shaping population viability and individual numbers and it is thought to change after habitat loss and fragmentation. The prediction is that specialized predators, dependent on a certain habitat type, should be more vulnerable to habitat loss compared to generalist predators, but habitat fragmentation effects are unknown.
In this presentation, I summarize the results from our predator - prey experiments conducted in experimentally fragmented habitat, created in to 0.25 ha small mammal proof enclosures. Enclosures consisted of either non-fragmented (one patch) or fragmented (four patches) habitat of the same total area surrounded by low vegetation matrix. We have been measuring the fragmentation effects on behaviour and fitness of prey species the bank vole (Myodes glareolus) and predator species the least weasel (Mustela nivalis nivalis) in a series of experiments.
We found that fragmentation led to increased matrix use in male voles and weasels, when resources were distributed into separate habitat patches. Small habitat fragments kept female bank voles closer to their nest where they were better able to protect pups against nest predators, infanticidal males. However, this did not affect the number of offspring recruited per female 1. Mammalian predator odor, a cue about increased predation risk in the habitat patches, decreased vole movements and voles directed movements towards matrix where the avian predation risk was higher 2. During high avian predation pressure, survival of male voles was poorer in fragmented habitat. Especially, males who moved most and spent time on open and risky matrix during radio -tracking were more likely to be depredated. Weasels killed more voles in the continuous habitat, which provided them safe hunting habitat from avian predators. However, this was only during autumn, when the kill rate was also higher due to cold weather 3.
To conclude, habitat fragmentation has direct survival and fitness consequences for individuals and it changes species interactions, but direction of these effects depend on fragmentation types and duration and scale of experiments.

1 Haapakoski M. et al. Infanticide effects on behavior of the bank vole (Myodes glareolus) in the fragmented breeding habitat. Behav Ecol Sociobiol 2015; 69: 49–59.
2 Haapakoski M. et al. Conservation implications of change in antipredator behavior in fragmented habitat: Boreal rodent, the bank vole, as an experimental model. Biol Conserv 2015; 184: 11–17.
3 Haapakoski M. et al. Mammalian predator-prey interaction in a fragmented landscape: Weasels and voles. Oecologia 2013; 173: 1227–1235.

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INTRO:
The authors give important information about the effects of habitat fragmentation on voles and weasels behaviour and survival, one of the more important threats on specialized species.

The first thing they found is that habitat fragmentation has behavioral effects on the bank vole (Myodes glareoulus). Females in fragmented habitats tend to move less and, therefore, stay nearer their nests than females in non-fragmented habitats. On the other hand, infanticidal males are more active in fragmented habitats, whilst non-infanticial males move more in continuous habitats. However, the recruitment rate of pups does not change between fragmented and non-fragmented habitats.

Habitat fragmentation is thought to alter predation-prey relationships. Under this hypothesis, authors address the effect of a higher predation risk on bank vole survival and behavior. They found that the perception of a predation risk decreases bank vole activity and have behavioural effects, reducing vole movement areas and increasing the use of the matrix (unsafe habitat), where increases the possibility of predation by avian predators.

Their last finding is related to the effects of habitat fragmentation on predator-prey relationships. The least weasel (a specialist predator) increases movements and hunting behavior in non-fragmented habitats and, therefore, vole mortality risk was higher in this kind of habitats. However, this pattern was not clear because it was not constant during the whole study period. It was observed only during the autumn season when energy demand increases.
MERITS:
This work elucidates some of the mechanisms underlying the negative impacts of habitat fragmentation. Habitat loss and fragmentation are the principal threats describe on wildlife populations but patterns of the effects are still lacking. Therefore, this work represents an important contribution to understand the effects of habitat fragmentation on wildlife populations. These findings contribute to the scientific knowledge and should be taking into account in the design of conservation measures and species re-introduction programmes.
CRITIQUE:
No weaknesses or problems
DISCUSSION:
As it was highlighted above, this work is an important contribution to the scientific knowledge about the effects of habitat fragmentation. However, as the authors have discussed before, it would be interesting to analyse the effect of an increase on predation risk without employing the yellow-necked mouse (Apodemus flavicollis) as a control species2. Other interactions such as competition might be hiding important effects of the least weasel (Mustela nivalis nivalis) predation risk on bank vole. On the other hand, in order to clarify the effects of habitat fragmentation on weasel hunting behavior it would be interesting to carry out the same study covering a longer a study period and with a higher sample of enclosures.

- - -
INTRO:
The study makes use of an experimental setup to investigate fragmentation effects on predator and prey species behaviour and their interaction. The study gives nice insights into the diverse effects of fragmentation on the different components of the system and allows interesting conclusions about fragmentation as a potential driving force for changes in predator-prey relationships.
MERITS:
The effects of habitat fragmentation are highly relevant for conservation biology. The experimental approach and the involvement of several species on two trophic levels makes this study an interesting contribution for understanding fragmentation effects on predator-prey systems. The abstract suggests including a large range of results from the investigated system for the talk and therefore likely gives comprehensive insights into the system.
CRITIQUE:
Altough it becomes clear when going back to the methods section, it would be nice to make the use of "matrix" in the following sentence even clearer by replacing it by e.g. "We found that fragmentation led to increased use of the vegetation matrix surrounding the fragmented habitat..."

It should be made clear from the beginning, that in addition to predatory weasels and prey voles the system also made use of birds as predators (and how they were included/excluded from the system). This would assist the understanding of the results that include birds as predators.
DISCUSSION:
Due to the high relevance of habitat fragmentation for conservation biology, the innovative experimental approach and the suggested comprehensive results to be presented, I support this talk as a contribution to ECCB 2018.

Habitat fragmentation and predation: Experiments with bank voles (Myodes glareolus) and least weasel (Mustela nivalis nivalis)

Date:2018/06/14

Time:10:00

Room:K306 Anton

Habitat fragmentation and predation: Experiments with bank voles (Myodes glareolus) and least weasel (Mustela nivalis nivalis)

(Oral and Poster)

SEE PEER REVIEW

SEE PEER REVIEW

Date:
2018/06/14

Time:
10:00

Room:
K306 Anton