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q-bio.PE · Populations and Evolutionstat.AP · Applications

Adult rodents at Portal, Arizona, were not lighter in warmer years and did not lose mass in 1977–2026 in 11 species; their hindfoot length decrease is mainly measurement drift

Question: are adult desert rodents lighter after warmer years, and did they become smaller during regional warming? Smith et al. (1998) found lower woodrat mass at higher temperature in New Mexico. Approach: we used Portal Project data release 6.117.0 (Arizona; monthly live trapping 1977-2026; 62,010 adult captures, 25,429 individuals, 11 species) and NOAA nClimDiv Cochise County climate (+0.26 °C per decade). For each species and year, we calculated an adjusted mean log mass and log hindfoot length, with sex, month and plot treatment fixed. We regressed the annual means on the mean temperature of the 12 months before capture, with log precipitation and a linear trend, and pooled the species with random effects. Results: the pooled mass slope was +2.7% per °C (95% CI +0.6 to +4.7). With year-to-year differences it was +1.7% (-0.6 to +4.0). In 30 model fits (other temperature sources and seasons, no rain term, males, females, control plots, first captures), the lowest lower CI limit was -2.04% per °C. Neotoma albigula was heavier in warmer years with year-to-year differences (+11.5% per °C, CI +5.7 to +17.4). The pooled mass trend was +0.57% per decade (+0.04 to +1.10). Hindfoot length decreased in all 11 species (pooled -1.0% per decade, CI -1.2 to -0.8). But the hindfoot year effects were synchronous across species (mean detrended pairwise r = 0.40, mass 0.15), and the changes in the same PIT-tagged adults followed the population changes (r = 0.70, 24 year pairs; summed change -5.5% within individuals, -4.9% in the population). Rounding to values that end in 0 or 5 also increased after 2020. Thus the hindfoot decrease is mainly a change in measurement, not in the animals. Limits: one site; temperature and precipitation are correlated (r = -0.62), and without the rain term the slope was +0.7% per °C (-0.4 to +1.8); mass drift from scales cannot be tested with the within-individual method.

body size · Bergmann's rule · climate warming · desert rodents · Portal Project · temperature-size rule · measurement drift · observer effects · Neotoma albigula · long-term monitoring · hindfoot length · space-for-time

Admitted 30 citing publications

References

10
  1. usesdoi:10.5281/zenodo.23574040

    Portal Project data release 6.117.0: individual rodent captures, weather station, plot treatments.

  2. usesdoi:10.1890/15-2115.1

    Data paper that describes the Portal Project design and methods.

  3. usesdoi:10.1175/JAMC-D-13-0248.1

    nClimDiv county temperature and precipitation used as the main climate series.

  4. usesdoi:10.1038/s41597-020-0453-3

    CRU TS 4.10 temperature used as a robustness check.

  5. challengesdoi:10.1111/j.1600-0587.1998.tb00668.x

    Reported lower Neotoma albigula mass at higher temperature in New Mexico; at Portal this species and the pooled 11 species were not lighter in warmer years.

  6. challengesdoi:10.1016/j.tree.2011.03.005

    Proposes declining body size as a general response to warming; adult mass at Portal did not decrease in 1977-2026.

  7. supportsdoi:10.7554/eLife.27166

    Found no general mass-temperature relationship within endotherm species; our temporal test agrees.

  8. doi:10.1038/s41598-020-65755-x

    Deer mouse body size trends with climate, including NEON data.

  9. Observer terms change the bird community temperature trend tenfold on 1,859 North American BBS routes (1970–2024), and within-observer declines are larger for high-pitched species sci:sha256:7895a5193624b2e131a63cb83531022a3859b2aa20011aea787f85ff0cc8a8f0

    Shows a similar problem: observer changes alter long-term trends in bird survey data.

  10. Year-to-year biomass responses of demersal fish to bottom temperature were about 3% of their spatial temperature slopes in 13 trawl survey units (1963–2023) sci:sha256:73ec8e55114714e88c3a1d65b19dc7fbadba02fb93318f40a435610325a52c6a

    Related test of year-to-year temperature responses in long-term survey data (demersal fish).

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