92 Kakui, The Swolhwittcj of Stouts hy Animals [ v«i. •? 



observed that the seals at least -can disgorge stones that have been swallowed, 

 md this is probably accounted for by their method of 'gulping* food, and 

 when digestion has reached a certain stage, being, enabled, naturally, to 

 regurgitate indigestible parts, which would include Slotted taken during the 

 •eanrh fnr foot! or at other times 



An interesting account of Ibis is given by C, A. I'leming (195U of 

 riooVers boa-lion, of pergonal experience* at the Auckland and Snares 

 islands, to the suult) of New Zealand. 



Tt is certain that the 'ballast* theory is fundamentally impossible and has 

 been used hy later writer* without ronsule.ra.tian. 



(l>) Aci'ideutitl 



The accidental theory could possibly account "or a small number of stones 

 being swallowed as seals seek their i<»nd m wali*r, and mi shallow waters 

 especially. 5tor.es are kept in lurbuleoct hy the waves. Tl*e walrus *inks to 

 the va floor, where, as almost standing on its head, H ploughs the hnttow. 

 moving in a backward direction, hi search of molluscs which Ituitow )l| the 

 nmd. 



Seal pup* have been seett to play with pehbles on ice floes, and the habit 

 of playing wiili nearby object* is not uncommon with the young ul must 

 animals. Lizards tcitud) and other reptiles eould swallow a few stone? 

 accidentally. Birds, ill a hurried search for food', have l^teh MKQ by the writer 

 ro pick: up and reject small stones and other inedible substances. Exception 

 to this are xtrulhious birds — moa. ostrich and CJBU 



(c) Sivi'tl-oivcd fyflh ft'Ofi nttitrhrd, i.e. st:ii-tmc)ntfH€\', <p>i.7<r,t f Wr 



This theory, simitar to The previous, could account for a small number of 

 srones in tl*e digestive system. Although many forms of the lower invertebrates 

 attach themselves to rocks, which may subsequently become dishxifted. iJiese 

 'O'tii a vwy srnall proportion of the food required by Ihe larger ~venehr*tc,%. 



<J) Already m the ictod sivaUyivdf, /v. fish, etc. 



This theory al<o. as in the two previous ones, Would account tor i-veii * 

 lesser number of gastroliths 



<<■) rVar'nY 'thrn-uu) Quiff 



This theory, whicli has been advanced in more recent years, mainly through 

 research work <M the p.r.uepodia in Australia, as well as in other countries, 

 appears to supply, in part, an answer to the problem as concerns the seal*. 

 sea-lions, and others of that group, it cannot, as yet, be used in the case 

 0J crocodiles or i|ie birds- 

 Research in connection wiih the Victorian seals has shown Ifyftt :»bouf 

 twenty -five per cent of seal? are attacked by parasitie worms; and, although 

 most of these afte^'ieti seah had stones if) then* stomachs, quite oftcu the 

 leverse was the case. 



Investigations ; m a ^ € occurrence of gastric ulcers in sea-imtnmaJs of the 

 coast of California, by C V.. Schrocdci and Tl, M Wegefonh £1-935), has 

 shown that these mammals swallow the sand of the Iicaches rlicy inhabit, 

 which, being composed of volcanic rocks nod containing obsidian (volcanic 

 ulass) is the cause of ulcers in the stontachs of die Ltephant Seat, Calltotuian 

 Sea lion, and the Galapagos Sea-lion. 



It is thought that possibly the; mammals swallowed the sand to allay 

 irritation caused by parasitic worms, but more probably the sand was uscil 

 lor trituration of their food, ll is worthy of mention that nematode parasite* 

 have been found in the stomachy of several of the MnUun-bml of Phillip 

 Island, Western Port Bay. Victoria, by the late Fred .Lewis (loc cit.). 



Another suggestion advanced by H. ttrartcr Howell 0930 b, is that as 

 Ihe male pinnepeds ro without food for several weeks i!uti!j>- the breeding 



