Seasonal role of a specialist predator in rodent cycles: Ermine-lemming interactions in the High Arctic

The exact mechanisms behind population cycles remain elusive. An ongoing debate centers on whether predation by small mustelids is necessary and sufficient to generate rodent cycles, as stipulated by the specialist predator hypothesis (SPH). Specifically, the SPH predicts that the predator should respond numerically to the abundance of its prey with a delay of approximately one year, leading to delayed density-dependence in the dynamics of the prey population. Here, we analyze the numerical response of a small mustelid, the seasonality of its interaction with rodents and its impact on population cycles using long-term seasonal data on ermines and cyclic lemmings in the High Arctic. Our results show that the numerical response of ermines to lemming fluctuations was delayed by one year and could mediate delayed density-dependence in lemming growth rate. The impact of ermines on the growth rate of lemmings was small but mostly circumscribed to winter, a critical period when shifts in cycle..., , , # Seasonal role of a specialist predator in rodent cycles: Ermine-lemming interactions in the High Arctic

[https://doi.org/10.5061/dryad.6t1g1jx7x](https://doi.org/10.5061/dryad.6t1g1jx7x)

## Description of the data and file structure

The data here provided covers different wildlife censuses conducted on Bylot Island, NU, Canada, between 1993 and 2022. These census are snap- or live-trapping of two species of lemmings (*Lemmus trimucronatus* &* Dicrostonyx groenlandicus*), transects to estimate winter nest densities and surveys of opportunistic observations to get an idea of ermine (*Mustela richardsonii*) abundance. Methods are well described in Fauteux et al., (2018) regarding lemming live trapping and winter nest and in Bolduc et al., (2023) for ermine abundance.     

### Files and variables

#### File: Densites\_BrunsVariables\_2004-2022.csv

**Description:** Densities of lemmings estimates from live-trapping on Bylot Island, NU, Canada.

##### Variables

* site: Site where ...