The mechanical properties of red deer antler bone when used in fighting

Abstract

SUMMARYWe assessed the hydration state of antlers and its effect on antler mechanical properties compared with wet femur. Red deer antlers were removed from the head at various times, from a few days after velvet shedding till late in the season, and weighed weekly until after casting time. Antlers cut just after losing their velvet lost weight rapidly in the first few weeks, then settled down and changed weight very little, the latter changes correlating with air relative humidity. Antlers cut later showed little weight change at any time. The water content of cortical and trabecular parts of the contralateral antler was assessed after cutting. Most of the weight loss was from the cancellous, not the cortical, part of the antler. Wet and dry specimens from the antlers, and wet specimens from deer femora, were tested mechanically. Compared with wet bone, wet antler had a much lower modulus of elasticity and bending strength, but a higher work to fracture. Compared with wet bone, dry antler showed a somewhat lower Young's modulus, but a considerably higher bending strength and a much higher work to fracture. The impact energy absorption of dry antler was much greater than that of wet bone. In red deer, the antler is effectively dry during its use in fights, at least in southern Spain. In addition, dry antler, compared with ordinary bone, shows mechanical properties that suit it admirably for its fighting function.

Programming function into mechanical forms by directed assembly of silk bulk materials

“…Silk fibroin fibers are renowned for their flexibility, which originates from the coordination of interfibrillar and intrafibrillar hydrogen bonds and from the molecular and nanoscale structure of the material that can be considered an amorphous matrix where crystalline β-sheet structures are embedded in highly ordered structures along the fiber's longitudinal axis (37). In the silk materials described in this study, the highly anisotropic nature of silk fibers is not maintained and the β-sheet nanocrystals are randomly oriented in the material, which impart a significant flexural strength comparable to some hierarchically structured tissues such as wet deer antler bone (38) or hard keratinaceous materials (39) (e.g., feather, claws, and nails). This remarkable similarity in the mechanical properties may be explained by a combination of (i) higher amount of free water in the tissues' structures (25-10 wt%) compared with <10 wt% of free water present in silk fibroin materials and (ii ) higher porosity of the biological tissues that result in the formation of a less dense structure, even if the density of silk, keratin, and collagen is similar (ρ ∼ 1.3-1.44 g/mL).…”

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

“…In winter, antlers fall off; this is known as shedding. Similar to bones, antlers contain pores and can withstand applied stresses of over 300 MPa (Landete-Castilleijos et al 2007b;Evans et al 2005;Akhtar et al 2008;Currey et al 2009), which is even higher than that of bones (Table 3). Therefore, antlers are occasionally considered an almost unbreakable bone ).…”

Inter-Specific Differences in the Structure and Mechanics but not the Chemical Composition of Antlers in Three Deer Species

“…The width and depth of each sample were recorded to the nearest 0.01 mm using a digital caliper. Tests were carried out with the periosteal side in tension (Currey et al 2009). During the period of active fighting, antlers have a moisture content similar to samples left at 'dry room' conditions and so mechanical testing was conducted at near dry conditions (Currey et al 2009).…”

“…Tests were carried out with the periosteal side in tension (Currey et al 2009). During the period of active fighting, antlers have a moisture content similar to samples left at 'dry room' conditions and so mechanical testing was conducted at near dry conditions (Currey et al 2009). In order to ensure a homogeneous humidity content, the samples were first hydrated in Hank's balanced buffer solution (HBSS BE10-527F; Lonza, Verviers, Belgium) for 48 h, and then left to dry at room temperature (20 °C) and humidity (40%) for another 48 h before testing.…”