Tag Archives: sex

Hvorfor er dyr hvor de er?

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.

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Why are animals where they are?

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.

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Water Pollution Allows Unhealthy Males to Breed More

Normally three spined sticklebacks are less likely to find a mate when they are affected with parasites, but does this change with eutrophication? (Image Credit: Sam Perrin, NTNU)

Reversed parasite-mediated selection in sticklebacks from eutrophied habitats (2010) Heuschele & Candolin, Behavioral Ecology and Sociobiology DOI: 10.1007/s00265-010-0937-9

The Crux

We’ve all heard the stories of turtles choking on plastic bags, or birds swallowing sporks. Algae grows out of control due to chemicals being added to the water, which changes the native habitat. For fish like sticklebacks, where males compete for the attention of females, the loss of visibility has the potential to be a problem for the females. Male sticklebacks defend a territory, develop a bright red spot, and fight other males. The long and short of it is that the bigger, stronger, and prettier fish mate more and the weaker and uglier fish don’t. One thing that weaker males tend to have more of than stronger males are parasites, which isn’t a surprise as a parasite’s entire existence revolves around surviving at the expense of whatever organism is unfortunate enough to have them.

Understanding how eutrophication affects female choice in relation to parasites, and thus the reproductive dynamics of this system, is quite important. This paper tries to map that out, using the Baltic Sea around Southern Finland. This experiment is well-suited to the problem, as there has already been evidence for algal growth changing the dynamics of stickleback reproduction.

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Bringing Back the Wolverine

The Swedish government changed tactics at the end of the 20th century, giving incentives to farmers when there were successful wolverine reproductions in their area

The Swedish government changed tactics at the end of the 20th century, giving incentives to farmers when there were successful wolverine reproductions in their area (Image Credit: Vojtěch Zavadil, CC BY-SA 3.0)

Paying for an Endangered Predator Leads to Population Recovery (2015) Persson et al., Conservation Letters, https://doi.org/10.1111/conl.12171

The Crux

Humans have a long history of driving dangerous predators out of their backyard. Wolves and wolverines have been driven out of different parts of Europe at different points in history at the behest of farmers looking to protect their livelihood, and the Tasmanian Tiger was driven to extinction for the same reason. But with the realisation that these predators bring enormous ecosystem benefits, governments have been searching for ways to bring about co-existence between predators and locals.

This study looks at a scheme introduced by a Swedish government in 1996, where reindeer herders had previously been compensated for any wolverine related losses. The new scheme introduced compensation for successful wolverine reproductions in the area. Persson et al. decided to have a look at how it fared.

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