THE SOUTHERN SEA LION, OTARIA 

 BYRONIA (DE BLAINVILLE) 



By J. E. Hamilton, M.Sc. 

 (Plates I-XIII; text-figs. 1-7) 



INTRODUCTION 



THE southern sea lion, Otaria byronia, has for long been well known to zoologists 

 so far as its structure and taxonomic position are concerned, but our knowledge 

 of its natural history has hitherto been of the scantiest. Since this seal is likely to prove 

 of some economic importance in the Falkland Islands, the Discovery Committee decided 

 to undertake an investigation of the species, and the present paper is based on obser- 

 vations and collections which I have made during the period from December 1929 to 

 March 1932. 



Before it can be considered that our knowledge of Otaria byronia is complete, so far 

 as the Falkland Islands are concerned, further information is still required on the 

 following heads : 



(i) Length of life of both sexes. 



(2) Rates of birth, death and increase. 



(3) Oestrous cycle and extreme limits of breeding season. 



(4) Habits of migration, if any. 



(5) Census of the herd in the Falklands. 



It would be invidious to name in particular any of the numerous friends in the 

 Falklands without whose help this work could never have been conducted: I wish 

 therefore to express my gratitude to them collectively. The Staff of the British Museum 

 (Natural History) has been most helpful on many occasions, and I would also express 

 my thanks to Mr R. H. Burne, F.R.S., the Curator of the Museum of the Royal College 

 of Surgeons, and to Dr A. S. Parkes, F.R.S., for valuable assistance. 



Reference is frequently made in the course of this report to Cape Dolphin. Cape 

 Dolphin forms the north-west point of East Falkland Island. It is the site of an 

 extensive sea-lion colony, and a considerable part of the work here described was 

 done there. 



HISTORICAL 



The southern sea lion is an Otariid of the largest size, and like all its congeners it is 

 gregarious and polygamous, and resorts to recognized breeding places at the appropriate 

 season of the year. It inhabits the coasts of South America from the Rio de la Plata 

 of the east side to about 4 degrees south latitude on the west, including the Galapagos 

 and Falkland Islands. In the latter it breeds in very large numbers. 



The sea lion is known to most of the inhabitants of the Falklands as the "seal", or 



