METHODS OF EAT DESTRUCTION. 24E 



Hunting loiih Dogs and Ferrets. 



Although this method is practically useless in most towns, it is- 

 of the greatest assistance in keeping down the rat population in 

 the country. A good ratting dog seldom fails to locate the 

 presence of a rat, and will always differentiate between the in- 

 habited and uninhabited holes. The I'esults obtained when ferrets- 

 co-operate with a dog are usually very satisfactory, and such hunts, 

 witih sticks and shot-guns in the Society's Gardens, in conjunc- 

 tion with trapping, has led in the past few years to a very 

 distinct reduction in the numbers of rats, in spite of the genei'al 

 increase elsewhere. The time spent on rat-hunting with the 

 help of dogs and ferrets has during the months of April to 

 Septeu)ber averaged eight hours a week aiid has resulted in 

 340 rats being killed. Like trapping, hunting with dogs and 

 ferrets should be pursued with special activity during the winter 

 months, and during the periods following poisoning with Squill 

 or Barium Cai-bonate. 



Gassing. 



This method has the distinct advantage over all others in that 

 it kills not only the adult rats but also the ne\vl}-born in their 

 nests. The gases most frequently advocated for rat-destruction 

 are Carbon Bisulphide, Hydrocyanic Acid, and Sulphur Dioxide. 

 Although both Carbon Bisulphide and Hydrocyanic Acid are very 

 effective, the dangerous nature of these gases, the former being 

 highly inflammable and explosive, and the latter very jDoisonous, 

 odourless, and invisible, makes it impossible to recommend their 

 use. Sulphur Dioxide, however, is visible and non-inflammable^ 

 and harmless to man when inhaled in small quantities. 



In the course of this summer we were a.fforded opportunities of 

 being present at fumiga.tions by means of sulphur candles, and 

 an apparatus maniifactui'ed by the Clayton Fire Extinguishing 

 and Disinfecting Company, in which the sulphur is burned in a 

 furnace supplied with air induced by a draught, and the gas 

 driven off under pressure through a hose. 



The use of the candles for killing ivats in their burrows we 

 found inefiective, the gas penetrating too slowly ; when the 

 sulphur dioxide is, however, driven into the holes under pressure 

 the whole network of runs is permeated in a few seconds, making 

 the existence of the rats underground impossible. Although 

 many of the rodents escape only to die in the open, some no doubt 

 recover, and the co-opei'ation of a dog is therefore desirable. The 

 large Clayton machines which are used for fumigating ships and 

 large buildings are driven by petrol or electricity. I was shown, 

 however, the model of a new portable hand-driven apparatus 

 which appeared suitable for the treatment of hedges and embank- 

 ments. IsTo opportunity Avas aflforded us of Avitnessing gassing 

 on shi]3S with these machines, but we were able to investigate 

 the system of rat destruction by means of sulphur candles as 



Proc. Zool. See— 1919, No. XVIII. 18 



