Pedicle and antler fusion and double-head formation in a sika stag (Cervus nippon)

Abstract

A case of pedicle and antler abnormality in a 12-14 year old sika stag shot in January 2003 in Schleswig-Holstein (Germany) is presented. The abnormality combines fusion of pedicles and antler bases with subsequent double-head formation. Double-heads result from growth of new antler bone without casting of the previous hard antlers. In consequence, two consecutively formed antlers are present in an individual. The stag's skull showed a plate-like osseous structure whose broad and slightly elevated central portion was identified as the fused pedicles. The peripheral parts of this osseous plate constituted the second antler growth of the (former) double-head. A cast pair of antlers, which were fused at their bases, had been found in a neighbouring hunting district in the summer of 2002. The close fit between the casting surface of the fused antlers and the surface of the pedicle/antler structure on the stag's skull indicated that the antlers had been grown by this stag and were belatedly cast from his fused pedicles. The fused antlers thus constituted the first antler growth of the doublehead. We suppose that the broad connection between the fused antlers and the fused pedicles prevented antler casting at the normal time and thereby caused the double-head condition. The presentation of this antler abnormality is taken as an occasion to discuss the significance of pedicles for the normal casting and regeneration of antlers.

The structure of pedicle and hard antler bone in the European roe deer (Capreolus capreolus): a light microscope and backscattered electron imaging study

“…A central biological function of pedicles is probably to ensure that the massive osteoclastic activity leading to antler casting occurs at a 'safe distance' from the skull roof. Moreover, pedicles provide a connection with a defined diameter between antler and skull that can effectively be eroded within the seasonal period of low androgen levels (Kierdorf et al 2004b).…”

“…Moreover, pedicles provide a connection with a defined diameter between antler and skull that can effectively be eroded within the seasonal period of low androgen levels (Kierdorf et al. ).…”

Trauma-induced malformed antler development in male white-tailed deer

“…Another 5 samples possessed malformed pedicles but suffered no apparent injuries to the actual cranium. Lastly, we documented several ≥3.5‐year‐old males with anomalies not fitting into one of the aforementioned categories—1 sample with pedicle located on the lateral side of the cranium, 1 specimen missing portions of the nasal and frontal bones due to prior trauma, 2 cases of accessory pedicles (Bubenik and Hundertmark ), and 1 case of “double‐head” antler formation (Kierdorf et al ).…”

“…Conversely, abnormal antlers due to cranial injury (skull or pedicle) often re‐aggravate because clean separation during antler casting is unlikely. This causes additional damage and leads to a greater chance of permanency (Kierdorf et al ); in fact, spike‐on‐one‐side antlers stemming from skull and/or pedicle trauma sometimes get progressively worse in successive seasons of antler development due to repeated injuries (Kierdorf et al ). Based on this knowledge, we recommend that yearling white‐tailed deer not be culled because of abnormal antler development for management purposes because immature male white‐tailed deer are likely to develop normal antlers in the future.…”

“…In adult white‐tailed deer, skull and/or pedicle damage is likely to be sustained through breeding activities such as fighting with conspecifics and rubbing trees (Bubenik et al ). When the antlerogenic periosteum is damaged, the pedicle may lose some of its structural integrity and strength, and during the healing process becomes fused with portions of the surrounding cranial region; this virtually ensures additional damage when antler casting occurs again (mechanism of re‐aggravation; Kierdorf et al ). Because far more antler abnormalities in older‐age‐class males are due to skull and/or pedicle trauma and these types of injures tend to re‐aggravate (Kierdorf et al ), spike‐on‐one‐side antlers are more likely permanent and repeated in subsequent years (Figs.…”