Convergent Evolution Driven by Similar Feeding Mechanics in Balaenopterid Whales and Pelicans

Abstract

The feeding apparatuses of rorqual whales and pelicans exhibit a number of similarities, including long, kinetic jaws that increase gape size, and extensible tissue comprising the floor of the mouth. These specializations enable the engulfment of large volumes of prey-laden water in both taxa. However, the mechanics of engulfment feeding in rorquals and pelicans have never been quantitatively compared. Here, we use ''BendCT,'' a novel analytical program, to investigate the mechanical design of rorqual and pelican mandibles, to understand whether these bones show comparable designs for resisting similar hydrodynamical loads. We also compare the mechanical properties of the extensible tissue used during engulfment in rorquals and pelicans. We demonstrate that the evolutionary convergence in the feeding apparatus of rorquals and pelicans is more pronounced than has been recognized previously; both taxa exhibit mandibular flexural rigidity distributions suited for resisting dorsoventral bending stresses encountered while feeding, and possess similarly extensible tissue on the floor of their mouths. Anat Rec, 294:1273Rec, 294: -1282Rec, 294: , 2011. V V C 2011 Wiley-Liss, Inc.

Vertebral bone microarchitecture and osteocyte characteristics of three toothed whale species with varying diving behaviour

“…In whales, regional variations in bone density have been observed in previous studies on humpback whales and at other skeletal sites, such as the mandible, where the bone geometry and density distribution are adapted to bending forces 27, 28 . In the spine, biomechanical simulation models are needed to further characterise the vertebral bone adaptations to swimming activity.…”

Feeding in billfishes: inferring the role of the rostrum from a biomechanical standpoint

“…The utility of these approaches has been demonstrated for experimentally intractable taxa, via investigations of feeding mechanics in white sharks, bull sharks and rorqual whales (Wroe et al, 2008;Field et al, 2011;Habegger et al, 2012). Significant advances in biomechanical studies have been accomplished through the utilization of beam theory, an engineering approach that describes the mechanical behavior of a beam under loading.…”

“…Because EI accounts for both material and structural properties, it is a useful metric for characterizing mechanical function in comparative studies, particularly when linking organismal function with evolutionary and ecological pressures (Koehl, 1976(Koehl, , 1977Macleod, 1980;Etnier, 2003). Flexural stiffness has been shown to correlate with loading regime and direction for a range of biological body support systems, from the limb skeletons of batoids and dogs, to the jaws of whales and pelicans, to the exoskeletons of crabs (Kemp et al, 2005;Taylor et al, 2007;Field et al, 2011;Macesic and Summers, 2012); these taxonomic comparisons also illustrate that higher levels of bending resistance can be attained evolutionarily by increases in either E or I, or in both.…”

Diet composition and provisioning rates of nestlings determine reproductive success in a subtropical seabird

“…Highly mobile marine predators employ a wide variety of foraging tactics, allowing them to exploit different prey types and forage in different sections of the water column (Ashmole 1971, Spear & Ainley 1998, Ballance & Pitman 1999. The plungediving brown pelican Pelecanus occidentalis employs a particularly distinctive high-volume foraging strategy, capturing large volumes of prey items simultaneously using a feeding method and jaw morphology more closely analogous to that of rorqual whales (Balaenopteridae) than that of other seabirds (Field et al 2011). Variation in prey capture strategies can play an important role in prey selection for predators that transport food to stationary young (i.e.…”

“…While raising young, pelicans feed mostly on fish by plunge-diving, and can transport large masses of fish in a single trip to provision nestlings (Field et al 2011). Brown pelicans nest in offshore colonies that can number from hundreds to thousands of nests, where they lay up to 3 sequentially hatching eggs at 2 d intervals, incubate eggs for approximately 30 d, and typically raise 1 to 2 young.…”