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Hvorfor er dyr hvor de er?

Posted on May 14, 2019 by Sam Perrin One comment

Image Credit: Endre Gruner Ofstad, CC BY-SA 2.0

Guest post by Endre Grüner Ofstad. English version here.

Use, selection, and home range properties: complex patterns of individual habitat utilization (2019) Endre Ofstad et al., Ecosphere, 10(4), https://doi.org/10.1002/ecs2.2695

Det essensielle

Stedene man finner dyr omtales gjerne som dyrets habitat. Habitat er et relativt vagt begrep. Hvor individ oppholder er som regel et utfall av en rekke vurderinger: hvor finner en mat, hvor unngår man rovdyr og hvor finner man noen å parre seg. Individ avveier blant disse for å maksimere hvor mange avkom de kan tilføre fremtidige generasjoner (også kalt for ‘fitness’).

Når vi skal vurdere hvilke habitat dyr befinner seg i så jobber vi som regel med habitatseleksjon. Habitatseleksjon er hvor mye et habitat blir brukt i forhold til hvor tilgjengelig det er, dvs. hva er den relative sannsynligheten for at et dyr vil bruke et habitat hvis det får muligheten. Hvor mye tid et individ velger å bruke (eller tettheten av individ) i et habitat er som regel en god indikator på hvor viktig et gitt habitat er. Habitatseleksjon blir derfor ofte brukt til å identifisere hvilke habitat forvaltningen bør iverksette tiltak.

Norwegian

Why are animals where they are?

Posted on May 8, 2019 by Sam Perrin One comment

Image Credit: Endre Gruner Ofstad, CC BY-SA 2.0

Guest post by Endre Grüner Ofstad. Norwegian version available here.

Use, selection, and home range properties: complex patterns of individual habitat utilization (2019) Endre Ofstad et al., Ecosphere, 10(4), https://doi.org/10.1002/ecs2.2695

The Crux

The areas in which we find an animal is often called its ‘habitat’. Yet it’s a fairly ambiguous term. Where animals are found is usually the outcome of a range of considerations, primarily foraging, predator avoidance and mating opportunities. Animals trade-off among these in order to maximise their contribution to future generations (i.e. ‘fitness’).

When considering which habitats we most likely find animals one often works with habitat selection. Habitat selection is how much a certain habitat type is used compared to its availability, i.e. what is the relative probability that an animal will use a given habitat upon encounter. The amount of time an individual spends (or density of individuals) in a habitat is usually a good proxy for the importance the habitat to the animals. Therefore we often use this to evaluate which areas to target for management and conservation efforts.

Paper of the Week

Population Trends in the Face of Climate Change

Posted on August 9, 2018 by Sam Perrin 2 comments

The Indian Pond Heron, one species which could face population declines as a result of climate change (Image Credit: Dr Raju Kasambe, CC BY-SA 4.0, Image Cropped)

Rapid warming is associated with population decline among terrestrial birds and mammals globally (2018) Spooner et al., Global Change Biology, DOI: 10.1111/gcb.14361

The Crux

The term climate change is almost ubiquitous these days. Humans tend to concentrate on how the warming of certain parts of the globe will affect them, but the species we share the globe with also experience a myriad of effects at the hands of climate change. These include rising temperatures constricting the ranges of some species and concurrently extending the range of others, who can move into areas that were previously too cold for them.

Whilst the focus of climate change has often been on species range shifts, the effects on species abundances are less well studied. This paper attempts to quantify the effects of climate change on a large number of bird and mammal species, whilst accounting for other factors which could affect species abundances, like rates of land use by humans, species body size, and whether or not the animals are in a protected area.