Abstract
Lagomorphs show extensive seasonal variation in their reproduction. However, the factors causing this large variation have so far mostly been investigated intraspecifically and therefore provide only some exemplary comparisons of lagomorph reproductive seasonality. The present study applies both a categorical description (birth season categories 1–5) and a quantitative measure (birth season length in months) to summarize the degree of birth seasonality in the wild of 69 lagomorph species. Using a comparative approach, I tested the influence of 13 factors, comprising six habitat, five life history and two allometric variables on birth season length in lagomorphs. Leporids mainly show non-seasonal birthing patterns with high intraspecific variation. Their opportunistic breeding strategy with high reproductive output and their large distribution areas across wide latitude and elevation ranges might be the reasons for this finding. Ochotonids reproduce strictly seasonally, likely because they live at northern latitudes, are high-altitude specialists, and occur in limited distribution areas. The most important factors associated with variation in lagomorph birth seasonality are mid-latitude, mean annual temperature and precipitation of a species’ geographical range and life history adaptations including fewer but larger litters in seasonal habitats. Birth seasons become shorter with increasing latitude, colder temperatures, and less precipitation, corresponding to the decreasing length of optimal environmental conditions. Leporid species with shorter breeding seasons force maternal resources into few large litters to maximise reproductive output while circumstances are favourable. Since allometric variables were only weakly associated with reproductive seasonality, life history adaptations and habitat characteristics determine birth seasonality in Lagomorpha.
Highlights
Reproduction is energetically very expensive for most organisms
To investigate which factors influence reproductive seasonality in the natural habitat of different lagomorphs, a broad dataset on birth seasonality covering 69 species was compiled from the literature
Each species was assigned to one of five birth seasonality categories based on its birthing pattern following (Zerbe et al 2012; Heldstab et al 2018, 2021; Heldstab 2021): Category 1: narrow peak, no births for the rest of the year; category 2: expanded peak (> 60 days) or double peak, no births for the rest of the year; category 3: peak(s) accompanied by a small number of births throughout the year; category 4: births throughout the year, undulating pattern. category 5: constant births throughout the year without a clear preferred season
Summary
Reproduction is energetically very expensive for most organisms. This is true for placental mammals, where females bear the metabolic costs of pregnancy and lactation (McNab 2006; Speakman 2008; Heldstab et al 2017). Lagomorphs show extensive seasonal variation in their reproduction. In some species, such as many pikas (Ochotonidae), all breeding activity takes place during a very restricted part of the year of only around one to two months (e.g., Chapman and Flux 1990; Smith et al 2018). In a fourth group of species, reproduction is entirely non-seasonal (Hayssen et al 1993; Wilson et al 2016)
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