Institute of Marine Science, University of California, Santa Cruz, CA, USA.
Hopkins Marine Station, Stanford University, Pacific Grove, CA, USA.
Nat Ecol Evol. 2023 Apr;7(4):535-546. doi: 10.1038/s41559-023-01993-2. Epub 2023 Mar 13.
Bulk filter feeding has enabled gigantism throughout evolutionary history. The largest animals, extant rorqual whales, utilize intermittent engulfment filtration feeding (lunge feeding), which increases in efficiency with body size, enabling their gigantism. The smallest extant rorquals (7-10 m minke whales), however, still exhibit short-term foraging efficiencies several times greater than smaller non-filter-feeding cetaceans, raising the question of why smaller animals do not utilize this foraging modality. We collected 437 h of bio-logging data from 23 Antarctic minke whales (Balaenoptera bonaerensis) to test the relationship of feeding rates (λ) to body size. Here, we show that while ultra-high nighttime λ (mean ± s.d.: 165 ± 40 lunges h; max: 236 lunges h; mean depth: 28 ± 46 m) were indistinguishable from predictions from observations of larger species, daytime λ (mean depth: 72 ± 72 m) were only 25-40% of predicted rates. Both λ were near the maxima allowed by calculated biomechanical, physiological and environmental constraints, but these temporal constraints meant that maximum λ was below the expected λ for animals smaller than ~5 m-the length of weaned minke whales. Our findings suggest that minimum size for specific filter-feeding body plans may relate broadly to temporal restrictions on filtration rate and have implications for the evolution of filter feeding.
批量过滤喂养使巨型动物在整个进化历史中得以生存。最大的动物，现存的须鲸，利用间歇性吞噬过滤喂养（吞吸），这种喂养方式随着体型的增大而效率提高，从而使它们得以巨型化。然而，现存最小的须鲸（7-10 米长的小须鲸），仍然表现出比小型非滤食性鲸类高出数倍的短期觅食效率，这就提出了一个问题，即为什么较小的动物不利用这种觅食方式。我们从 23 头南极小须鲸（Balaenoptera bonaerensis）收集了 437 小时的生物记录数据，以测试摄食率（λ）与体型的关系。在这里，我们表明，虽然夜间超高的 λ（平均值±标准差：165±40 次吞吸 h；最大值：236 次吞吸 h；平均深度：28±46 米）与从较大物种观察到的预测值无法区分，但白天的 λ（平均深度：72±72 米）仅为预测值的 25-40%。两种 λ 都接近计算出的生物力学、生理学和环境限制允许的最大值，但这些时间限制意味着最大 λ 低于预期的小于~5 米的动物的 λ——即断奶小须鲸的长度。我们的发现表明，特定过滤喂养身体计划的最小尺寸可能与过滤速率的时间限制广泛相关，并对过滤喂养的进化产生影响。
