4.2 Ageing, kill-off patterns and seasonality

Using age estimations derived from epiphyseal fusion and osteometric analysis, two main age groups of harp seals, yearlings and adults, are represented in Neustadt. The same pattern was recognised for grey seals. In order to retrieve information on seasonality of hunting patterns, data on ecology and biology were derived from modern harp and grey seal populations. According to data from extant harp seal populations, females give birth on pack ice in February/March (Sergeant 1991). If a similar breeding pattern is assumed for prehistoric harp seal populations in the Baltic Sea, then the seal pups up to 3 months old represented in the Neustadt assemblage must have been hunted during the spring. The yearlings up 10-11 months old must have been hunted in the late autumn. If prehistoric and modern harp seal populations share the same migration patterns, then two different seasons of hunting, which depict the annual life-cycle of this highly migratory species and correspond to the two annual migration phases, can be recognised. One occurs in late spring: after they have formed their moulting rookeries and the moulting is completed, they migrate to the summer feeding grounds (Lavigne and Kovacs 1988). The second migration takes place in early winter when they return to their breeding grounds to form their large breeding colonies (Lavigne and Kovacs 1988; Sergeant 1991). It is far from clear in which season adult seals could have been captured, because ageing of young adults and adult animals can only be a rough estimation. Nevertheless, it is highly likely that adult harp seals were captured during the same seasons and in the same regions as the yearlings and juveniles because harp seals of all ages show similar social behaviour and migration patterns and consequently are likely to have been present and captured in the same seasons and in the same regions as the youngest ones. Furthermore, even if it is not possible to distinguish males from females osteologically, it is highly possible that some of the adult seals represent females captured during the breeding season together with their pups.

Grey seals are not migratory; they usually stay in the proximity of their breeding grounds and therefore adult grey seals might have been captured any time of the year. More precise information on the seasonal hunting of grey seals again highlights the yearlings age group. Within this age group 10-11 month old grey seals are apparent. Three modern grey seal populations, in the western North Atlantic, in the eastern North Atlantic and in the Baltic Sea, exist independently of each other and give birth at different times of the year (Curry-Lindahl 1970; Anderson 1992). Judging from the modern grey seal populations in the Baltic Sea, which give birth in February-March (Curry-Lindahl 1970; King 1983), we can estimate a hunting season in late autumn for these seals.

Since ringed seal is represented by just a few bones it is not possible to retrieve any secure data about seasonality.

Apart from seals, marine mammals are represented at the site by a small number of bones from cetaceans. The lack of information on the ageing of cetaceans based on epiphyseal fusion data means that the age at death for either harbour porpoises or dolphins cannot be determined. The only information provided is based on a great number of unfused epiphyses from harbour porpoises, which indicates that these animals had not reached their full growth.