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Pollock TI, Hocking DP, Evans AR. Is a blunt sword pointless? Tooth wear impacts puncture performance in Tasmanian devil canines. J Exp Biol 2024; 227:jeb246925. [PMID: 38099427 PMCID: PMC10917061 DOI: 10.1242/jeb.246925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 12/07/2023] [Indexed: 02/01/2024]
Abstract
As teeth wear, their shapes change and functional features can be dulled or lost, presumably making them less effective for feeding. However, we do not know the magnitude and effect of this wear. Using Tasmanian devil canines as a case study, we investigated the impact of wear on puncture in pointed teeth. We measured aspects of shape impacted by wear (tip sharpness, height and volume) in teeth of varying wear followed by 3D printing of real and theoretical forms to carry out physical puncture tests. Tooth wear acts in two ways: by blunting tooth tips, and decreasing height and volume, both of which impact performance. Sharper tips in unworn teeth decrease the force and energy required to puncture compared with blunter worn teeth, while taller unworn teeth provide the continuous energy necessary to propagate fracture relative to shorter worn teeth. These wear-modulated changes in shape necessitate more than twice the force to drive worn teeth into ductile food and decrease the likelihood of puncture success.
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Affiliation(s)
- Tahlia I. Pollock
- The Palaeobiology Research Group, School of Earth Sciences, University of Bristol, Bristol BS8 1QU, UK
- School of Biological Sciences, Monash University, Melbourne, VIC 3800, Australia
| | - David P. Hocking
- School of Biological Sciences, Monash University, Melbourne, VIC 3800, Australia
- Department of Zoology, Tasmanian Museum and Art Gallery, Hobart, TAS 7000, Australia
| | - Alistair R. Evans
- School of Biological Sciences, Monash University, Melbourne, VIC 3800, Australia
- Museums Victoria Research Institute, Museums Victoria, Melbourne, VIC 3001, Australia
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Rule JP, Duncan RJ, Marx FG, Pollock TI, Evans AR, Fitzgerald EM. Giant baleen whales emerged from a cold southern cradle. Proc Biol Sci 2023; 290:20232177. [PMID: 38113937 PMCID: PMC10730287 DOI: 10.1098/rspb.2023.2177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 11/22/2023] [Indexed: 12/21/2023] Open
Abstract
Baleen whales (mysticetes) include the largest animals on the Earth. How they achieved such gigantic sizes remains debated, with previous research focusing primarily on when mysticetes became large, rather than where. Here, we describe an edentulous baleen whale fossil (21.12-16.39 mega annum (Ma)) from South Australia. With an estimated body length of 9 m, it is the largest mysticete from the Early Miocene. Analysing body size through time shows that ancient baleen whales from the Southern Hemisphere were larger than their northern counterparts. This pattern seemingly persists for much of the Cenozoic, even though southern specimens contribute only 19% to the global mysticete fossil record. Our findings contrast with previous ideas of a single abrupt shift towards larger size during the Plio-Pleistocene, which we here interpret as a glacially driven Northern Hemisphere phenomenon. Our results highlight the importance of incorporating Southern Hemisphere fossils into macroevolutionary patterns, especially in light of the high productivity of Southern Ocean environments.
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Affiliation(s)
- James P. Rule
- School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia
- Sciences, Museums Victoria Research Institute, Museums Victoria, Melbourne, Victoria 3001, Australia
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
| | - Ruairidh J. Duncan
- School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia
- Sciences, Museums Victoria Research Institute, Museums Victoria, Melbourne, Victoria 3001, Australia
| | - Felix G. Marx
- Museum of New Zealand Te Papa Tongarewa, Wellington 6011, New Zealand
- Department of Geology, University of Otago, Dunedin 9016, New Zealand
| | - Tahlia I. Pollock
- School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia
- Department of Anatomy and Developmental Biology, Monash University, Victoria, Australia
| | - Alistair R. Evans
- School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia
- Sciences, Museums Victoria Research Institute, Museums Victoria, Melbourne, Victoria 3001, Australia
| | - Erich M.G. Fitzgerald
- School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia
- Sciences, Museums Victoria Research Institute, Museums Victoria, Melbourne, Victoria 3001, Australia
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
- National Museum of Natural History, Smithsonian Institution, Washington, DC 20013, USA
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Marx FG, Hocking DP, Park T, Pollock TI, Parker WMG, Rule JP, Fitzgerald EMG, Evans AR. Suction causes novel tooth wear in marine mammals, with implications for feeding evolution in baleen whales. J MAMM EVOL 2023. [DOI: 10.1007/s10914-022-09645-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Pollock TI, Panagiotopoulou O, Hocking DP, Evans AR. Taking a stab at modelling canine tooth biomechanics in mammalian carnivores with beam theory and finite-element analysis. R Soc Open Sci 2022; 9:220701. [PMID: 36300139 PMCID: PMC9579775 DOI: 10.1098/rsos.220701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 09/30/2022] [Indexed: 06/16/2023]
Abstract
Canine teeth are vital to carnivore feeding ecology, facilitating behaviours related to prey capture and consumption. Forms vary with specific feeding ecologies; however, the biomechanics that drive these relationships have not been comprehensively investigated. Using a combination of beam theory analysis (BTA) and finite-element analysis (FEA) we assessed how aspects of canine shape impact tooth stress, relating this to feeding ecology. The degree of tooth lateral compression influenced tolerance of multidirectional loads, whereby canines with more circular cross-sections experienced similar maximum stresses under pulling and shaking loads, while more ellipsoid canines experienced higher stresses under shaking loads. Robusticity impacted a tooth's ability to tolerate stress and appears to be related to prey materials. Robust canines experience lower stresses and are found in carnivores regularly encountering hard foods. Slender canines experience higher stresses and are associated with carnivores biting into muscle and flesh. Curvature did not correlate with tooth stress; however, it did impact bending during biting. Our simulations help identify scenarios where canine forms are likely to break and pinpoint areas where this breakage may occur. These patterns demonstrate how canine shape relates to tolerating the stresses experienced when killing and feeding, revealing some of the form-function relationships that underpin mammalian carnivore ecologies.
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Affiliation(s)
- Tahlia I. Pollock
- School of Biological Sciences, Monash University, Clayton 3800, Australia
| | - Olga Panagiotopoulou
- Monash Biomedicine Discovery Institute, Department of Anatomy & Developmental Biology, Monash University, Clayton 3800, Australia
| | - David P. Hocking
- School of Biological Sciences, Monash University, Clayton 3800, Australia
- Zoology, Tasmanian Museum and Art Gallery, Hobart, Australia
| | - Alistair R. Evans
- School of Biological Sciences, Monash University, Clayton 3800, Australia
- Geosciences, Museums Victoria, Melbourne, Victoria, Australia
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Pollock TI, Hocking DP, Hunter DO, Parrott ML, Zabinskas M, Evans AR. Torn limb from limb: the ethology of prey-processing in Tasmanian devils (Sarcophilus harrisii). Aust Mammalogy 2022. [DOI: 10.1071/am21006] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The success of carnivorous mammals is determined not only by their ability to locate and kill prey, but also their efficiency at consuming it. Breaking large prey into small pieces is challenging due to the strong and tough materials that make up a carcass (e.g. hide, muscle, and bone). Carnivores therefore require a diverse suite of prey-processing behaviours to utilise their catch. Tasmanian devils are Australia’s only large marsupial scavengers and have the ability to consume almost all of a carcass. To determine how they do this we analysed 5.5 hours of footage from 21 captive and wild devils feeding at carcasses. We documented 6320 bouts of 12 distinct prey-processing behaviours, performed at frequencies that varied throughout feeds and between groups. The time point in the feed influenced the types of behaviours used. This is likely due to changing prey size, as different techniques appear better suited to handling whole carcasses or large pieces (pulling and pinning) or smaller pieces (holding and manipulating). Group size impacted the frequency of social pulling behaviours, which increased with the number of animals. Our findings highlight the range of prey-processing behaviours performed by scavenging devils when handling, breaking down, and consuming a carcass. The devils’ repertoire shares similarities with large carnivores that handle and consume whole carcasses as well as small carnivores that are adept in grasping and handling smaller prey.
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Pollock TI, Hunter DO, Hocking DP, Evans AR. Eye in the sky: observing wild dingo hunting behaviour using drones. Wildl Res 2022. [DOI: 10.1071/wr22033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Abstract
Abstract
Often the first point of contact between predator and prey, mammalian canine teeth are essential for killing, dismembering and consuming prey. Yet despite their importance, few associations among shape, function and phylogeny are established. We undertook the first comprehensive analysis of canine tooth shape across predatory mammals (Carnivora, Didelphimorphia and Dasyuromorphia), integrating shape analysis with function of this fundamental feature. Shape was quantified using three-dimensional geometric morphometrics and cross-sectional sharpness. Canines vary in three main ways (sharpness, robustness and curvature) which vary with diet, killing behaviour and phylogeny. Slender, sharp canines are associated with carnivores such as felids that target the neck of their prey and primarily consume the ‘softer’ parts of a carcass. Robust, blunt canines are found in mustelids and dasyurids that typically consume ‘harder’ materials, such as bone, or bite into skulls. Differences in the killing behaviours of felids and canids probably result in more curved canines in the latter, which act as hooks to hold prey. We find functional specialization in the upper and lower canines of individuals and across the major mammalian clades. These patterns demonstrate how canine teeth are adapted to suit diverse diets and hunting styles, enabling mammals to become some of nature's most successful predators.
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Affiliation(s)
- Tahlia I Pollock
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - David P Hocking
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
- Zoology, Tasmanian Museum and Art Gallery, Hobart, Tasmania, Australia
| | - Alistair R Evans
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
- Geosciences, Museums Victoria, Melbourne, Victoria, Australia
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Pollock TI, Parrott ML, Evans AR, Hocking DP. Wearing the devil down: Rate of tooth wear varies between wild and captive Tasmanian devils. Zoo Biol 2021; 40:444-457. [PMID: 34101216 DOI: 10.1002/zoo.21632] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 04/15/2021] [Accepted: 05/20/2021] [Indexed: 01/28/2023]
Abstract
Mammalian carnivores rely on their sharp teeth to effectively kill and consume prey. However, over time this causes wear and breakage that alters tooth shape, reducing their effectiveness. Extreme tooth wear and damage is especially prevalent in species that scavenge carcasses, like the Tasmanian devil (Sarcophilus harrisii), which are well known for their voracious appetites and ability to consume almost all of a carcass, including bone. In this study, we comprehensively describe tooth wear in captive and wild devils to look for differences in the patterns and rate of wear between these environments. To do this we surveyed tooth condition in skulls from 182 wild and 114 captive devils for which age was estimated using canine over-eruption. We found the types of tooth wear documented were the same in captive and wild devils, but captive animals have less severe wear than wild devils of the same estimated age. There was no difference in the proportion of captive or wild individuals with broken canine or molar teeth; however, breakage occurred at a younger age in wild devils. Although not considered anomalous or harmful, this indicates a difference in the way teeth are being used and/or the foods consumed between captive and wild devils. We hypothesize how these results relate to differences in diet or behavior that may stem from their various feeding environments, for example, higher quality food (fresh, whole, and yet to be scavenged carcasses) provided to captive devils likely causes less wear. Further, we support management options that closely replicate wild diet items and behaviors suitable for a long-term insurance population.
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Affiliation(s)
- Tahlia I Pollock
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - Marissa L Parrott
- Wildlife Conservation and Science, Zoos Victoria, Elliott Avenue, Parkville, Victoria, Australia
| | - Alistair R Evans
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia.,Geosciences, Museums Victoria, Melbourne, Victoria, Australia
| | - David P Hocking
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
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Evans AR, Pollock TI, Cleuren SGC, Parker WMG, Richards HL, Garland KLS, Fitzgerald EMG, Wilson TE, Hocking DP, Adams JW. A universal power law for modelling the growth and form of teeth, claws, horns, thorns, beaks, and shells. BMC Biol 2021; 19:58. [PMID: 33781258 PMCID: PMC8008625 DOI: 10.1186/s12915-021-00990-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 02/22/2021] [Indexed: 11/29/2022] Open
Abstract
Background A major goal of evolutionary developmental biology is to discover general models and mechanisms that create the phenotypes of organisms. However, universal models of such fundamental growth and form are rare, presumably due to the limited number of physical laws and biological processes that influence growth. One such model is the logarithmic spiral, which has been purported to explain the growth of biological structures such as teeth, claws, horns, and beaks. However, the logarithmic spiral only describes the path of the structure through space, and cannot generate these shapes. Results Here we show a new universal model based on a power law between the radius of the structure and its length, which generates a shape called a ‘power cone’. We describe the underlying ‘power cascade’ model that explains the extreme diversity of tooth shapes in vertebrates, including humans, mammoths, sabre-toothed cats, tyrannosaurs and giant megalodon sharks. This model can be used to predict the age of mammals with ever-growing teeth, including elephants and rodents. We view this as the third general model of tooth development, along with the patterning cascade model for cusp number and spacing, and the inhibitory cascade model that predicts relative tooth size. Beyond the dentition, this new model also describes the growth of claws, horns, antlers and beaks of vertebrates, as well as the fangs and shells of invertebrates, and thorns and prickles of plants. Conclusions The power cone is generated when the radial power growth rate is unequal to the length power growth rate. The power cascade model operates independently of the logarithmic spiral and is present throughout diverse biological systems. The power cascade provides a mechanistic basis for the generation of these pointed structures across the tree of life. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-00990-w.
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Affiliation(s)
- Alistair R Evans
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia. .,Geosciences, Museums Victoria, Melbourne, Victoria, 3001, Australia.
| | - Tahlia I Pollock
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia
| | - Silke G C Cleuren
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia
| | - William M G Parker
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia
| | - Hazel L Richards
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia
| | - Kathleen L S Garland
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia
| | - Erich M G Fitzgerald
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia.,Geosciences, Museums Victoria, Melbourne, Victoria, 3001, Australia
| | - Tim E Wilson
- School of Mathematical Sciences, Monash University, Melbourne, Victoria, 3800, Australia
| | - David P Hocking
- School of Biological Sciences, Monash University, Melbourne, Victoria, 3800, Australia.,Geosciences, Museums Victoria, Melbourne, Victoria, 3001, Australia
| | - Justin W Adams
- Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, 3800, Australia
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Hocking DP, Marx FG, Sattler R, Harris RN, Pollock TI, Sorrell KJ, Fitzgerald EMG, McCurry MR, Evans AR. Clawed forelimbs allow northern seals to eat like their ancient ancestors. R Soc Open Sci 2018; 5:172393. [PMID: 29765684 PMCID: PMC5936949 DOI: 10.1098/rsos.172393] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 03/13/2018] [Indexed: 05/31/2023]
Abstract
Streamlined flippers are often considered the defining feature of seals and sea lions, whose very name 'pinniped' comes from the Latin pinna and pedis, meaning 'fin-footed'. Yet not all pinniped limbs are alike. Whereas otariids (fur seals and sea lions) possess stiff streamlined forelimb flippers, phocine seals (northern true seals) have retained a webbed yet mobile paw bearing sharp claws. Here, we show that captive and wild phocines routinely use these claws to secure prey during processing, enabling seals to tear large fish by stretching them between their teeth and forelimbs. 'Hold and tear' processing relies on the primitive forelimb anatomy displayed by phocines, which is also found in the early fossil pinniped Enaliarctos. Phocine forelimb anatomy and behaviour therefore provide a glimpse into how the earliest seals likely fed, and indicate what behaviours may have assisted pinnipeds along their journey from terrestrial to aquatic feeding.
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Affiliation(s)
- David P. Hocking
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
- Geosciences, Museums Victoria, Melbourne, Victoria, Australia
| | - Felix G. Marx
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
- Geosciences, Museums Victoria, Melbourne, Victoria, Australia
- Directorate of Earth and History of Life, Royal Belgian Institute of Natural Sciences, Brussels, Belgium
| | | | - Robert N. Harris
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, UK
| | - Tahlia I. Pollock
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - Karina J. Sorrell
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - Erich M. G. Fitzgerald
- Geosciences, Museums Victoria, Melbourne, Victoria, Australia
- National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
- Department of Life Sciences, Natural History Museum, London, UK
| | - Matthew R. McCurry
- Australian Museum Research Institute, Sydney, New South Wales, Australia
- PANGEA Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Alistair R. Evans
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
- Geosciences, Museums Victoria, Melbourne, Victoria, Australia
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