UNIVERSITY OF CALIFORNIA AGRICULTURAL EXPERIMENT STATION BENJ. IDE WHEELER, PRESIDENT THOMAS FORSYTH HUNT, Dean and UirectoK BERKELEY H. E. VAN NORMAN, vice-director ano Dean University Farm School COLLEGE OF AGRICULTURE CIRCULAR No. 181 November, 1917 CONTROL OF THE CALIFORNIA GROUND SQUIRREL By JOSEPH DIXON (Contribution from the Museum of Vertebrate Zoology of the University of California) The ground squirrels are undoubtedly the most widely known and at the same time the most disliked mammals in California. The large, long-tailed, grayish-brown species known as the California or Fig. 1 .^Diagram showing methods of destroying ground squirrels to be employed at different seasons of the year. "digger" squirrel (Citellus beecheyi and subspecies) is of chief im- portance in its relation to man; first, because of its destructiveness to crops ; second, because it is a carrier of disease ; and third, because of the damage done by it to irrigation works. Three races of the digger squirrel occur within the state : the dark-colored northern form (the Douglas ground squirrel) which ranges from San Francisco Bay northward throughout that portion of the state which lies west and north of the Sacramento • and Feather rivers; the brownish Beechey ground squirrel which occupies central California and the coast district south from the Golden Gate; and the gray-toned Fisher ground squirrel whose habitat lies in the south- ern San Joaquin and Owens valleys and to the south throughout southern California. The characters which serve to distinguish these different races are not of any particular importance in relation to the work of eradicating these pests, so that from this standpoint the three forms may be considered as one. A knowledge of certain habits of feeding, breeding and hibernation possessed by these animals is of the greatest importance in control work and these habits are con- sidered at some length in the following pages. NATURE AND EXTENT OF DAMAGE According to Dr. C. Hart Merriam, of the United States Biological Survey, the national loss to agriculture through depredations of ground squirrels amounts to at least 10 million dollars annually. No other state suffers more, or as much, in this regard, as California. The loss due to the ground squirrel in California alone has been placed at as high a figure as that given above for the entire country, so that it is a conservative estimate to put the annual loss due to ground squirrels in this state as not less than five million dollars. The California ground squirrel occurs in troublesome numbers in most of the best farming and fruit-raising districts of the state. It is a voracious feeder and reproduces rapidly. Practically all kinds of grain and many kinds of fruit are subject to its depredations. This squirrel prefers an elevated location for its homesite, and in digging burrows it often honeycombs the banks of irrigation ditches, with disastrous results. .The ground squirrel is a carrier and disseminator of bubonic plague. Between May, 1907, and September, 1912, over 1000 plague- infected ground squirrels were examined from a single county in the San Francisco Bay region by the United States Public Health Ser- vice. While the immediate danger of acquiring the plague through ground squirrels seems to have largely passed, their destruction would surely tend to prevent the recurrence of danger on this score. FEEDING HABITS California ground squirrels have membranous cheek-pouches which open inside the mouth and are used to carry food, principally grain, to the underground store rooms. These cheek-pouches are not lined with fur as are those of the pocket gopher, but have thin walls which readily absorb the strychnine on the outside of poisoned grain. It has been demonstrated that ground squirrels are more readily poisoned through these cheek-pouches by merely carrying poisoned grain, than through the stomach after they have eaten it. For this reason the coated grain is preferred to that which has been soaked in a strychnine solution. The food and feeding habits of ground squirrels vary greatly with the locality and season of the year. During the rainy season, from November to April, although they utilize some grain, seeds or nuts that have been stored up during the previous summer, their main reliance is upon grass and other green herbage. This results in a very serious loss in many localities, as it greatly reduces the pasturage available for horses and cattle. "When green stuff is abundant, com- paratively little food is carried in the cheek-pouches. However, by the last of March certain plants, such as alfilaria, have begun to go to seed, and the squirrels then begin to use their cheek-pouches exten- sively in harvesting these seeds. At this time the squirrels take the poisoned grain readily, but later in the season when the cultivated grain begins to ripen they are much harder to poison on account of the abundant grain supply then available. Ground squirrels are very fond of the soft pits of peaches, almonds and apricots, and in getting these they destroy much fruit. On the whole, however, the principal loss from ground squirrels is in the grain fields, where the animals dig up and destroy the sprouting seed and later pull down and destroy a vast amount of the ripening grain. After the crops are harvested they congregate about the shocks and stacks and continue to devour and carry off quantities of grain. At this time watermelon rinds poisoned with strychnine are extremely effective, since succulent green food is scarce. AESTIVATION OF THE GROUND SQUIRREL There is evidence to support the belief that a period of aestivation, or state of torpidity induced by the heat and dryness of summer, obtains among some of the adult ground squirrels in the valleys of California. This period of dormancy extends from late summer well through midwinter, and thus involves hibernation as well as aestiva- tion. The old adults seem to be the only ones that ' ' hole up, ' ' for the young adults (somewhat over a year old) and the young of the year may be seen about the burrows during suitable weather throughout the winter. A close and continuous watch, extending "over several years, was kept on a female ground squirrel that lived under normal conditions in the dooryard at the home of Mrs. Elizabeth Grinnell in Pasadena. These observations brought forth the following facts. This particular squirrel did not aestivate until its second year. Then and during each succeeding year of its life it aestivated regularly, becoming very fat and retiring to its burrow during the last week in August. The squirrel emerged in an emaciated condition, with marked regularity, about the 22nd of each following February. When removed from the burrow during this period, this animal was found to be in a torpid state and respiration was not perceptible. This habit of aestivation affords explanation of a case in the author's experience, in which all the squirrels that were active in a certain field in the fall were poisoned or killed, and yet old breeding squirrels suddenly appeared in this same field the following February. This state of affairs occurred when there was seemingly no possible chance for re-infestation from the surrounding fields. The extent of this habit of aestivation among our ground squirrels is unknown. It is ex- ceedingly difficult to follow any individual squirrel through all its various activities for any great length of time. However, an im- portant factor concerned in the work of destroying these animals is suggested; that is, the desirability of placing emphasis upon the need of poisoning in the spring rather than in the fall when some of the breeding stock may be stowed away out of the reach of poisoned grain. It is a question, too, whether or not a dormant animal, in which respiration is extremely slow, would be fatally injured by a fumigant before the latter would disappear. TIME AND RATE OF BREEDING The accompanying chart (fig. 2) is based on over 10,000 female squirrels examined by the United States Public Health Service during the spring and summer of 1910, and proves that the California ground squirrel has a very definite breeding season and that this period begins about the first of February and lasts until the first of May. The maximum number of pregnant females was found during the week ending February 26. The bulk of the young are born about five weeks after this date and may be seen running about at the entrances of the burrows a month or six weeks after they are born. In low, warm valleys the breeding season has been found to be somewhat earlier than the above averages would indicate, while along the coast and in the mountains the breeding season is about two weeks later than the dates given. The usual annual increase of a pair of ground squirrels consists of one litter of from five to eleven young. The average number of embryos in pregnant females was found by the United States Public Jan. Feb. Mar. Apr. moy AZ 10 36 36 34 32 30 26 26 24 22 20 16 16 14 IZ 10 8 6 4 2 22 29 5 -iZ /9 2 6 6 12 19 26 2. 9 /6 23 30 7 14 :r 1 k it \ iA 1 I \ t / \ \ i t \ *" T \ i \ J \ i \ / \ ^ i " ■»<, / [S i I ■» % / i \ _£ / / \ f / \ \ / i \ \ * ' i \ \ i \ I i \ / k- - \^_ / i i ^ N \ f i \ Fig. 2. — Chart showing breeding season of California ground squirrels. (Com- piled chiefly from data obtained from United States Public Health Eeports, vol. 27, July 5, 1917, p. 1070.) Figures in left-hand column represent per cent of females found pregnant; over 10,000 females examined. Eepresents preva- lence of pregnacy among female ground squirrels between January 15 and May 14. For example, during the week ending March 5, 27 per cent of females examined were pregnant. Shows approximately the time of birth of the bulk of young squirrels. Health Service to be 7.2. There is some evidence to indicate that a second litter is sometimes raised in a single season, but this is surely not the usual thing The important point to be noted in this connec- tion is that one breeding female killed before April 1, that is, before the young are able to take care of themselves, is equal to the destruc- tion of from six to twelve squirrels later in the season. A wise man will go after the squirrels early in the year, when "a stitch in time" will literallv "save nine." METHODS OF CONTROL The five most effective methods of destroying ground squirrels are : (1) poisoning with strychnine; (2) fumigation with carbon bisul- phide; (3) trapping; (4) shooting; (5) encouragement of the natural enemies of the ground squirrel. WHICH METHOD TO USE, WHEN, AND WHY (See Fig. 1) i. Carbon bisulphide is most effective when the soil is damp. When the ground is dry the gas escapes through the cracks in the ground. 2. Strychnine-coated barley is best used during the dry season because at this time the squirrels gather and store grain and hence are easily poisoned through their cheek pouches when in the act of carrying the poisoned grain. Rain and heavy fogs tend to wash the strychnine off the poisoned grain. 3. Trapping and shooting are effective at any time, but are from six to twelve times more so before the young are out, before April 1, than later in the season. 4. Powdered strychnine (sulphate) in fresh vegetables and fruit is especially effective in the dry season when green food is scarce. 5. Red-tailed hawks, Golden eagles, badgers, weasels, and other natural enemies of the ground squirrel will prove valuable allies in the war on ground squirrels if they are only allowed to live. It costs little to let them alone, to go about their business in the natural way. COMPARATIVE COST OF VARIOUS METHODS In 1910, Dr. C. Hart Merriam 1 gave the cost of one treatment with poisoned grain as 3 cents per acre and for one treatment with carbon bisulphide ("waste-ball" method) at iy 2 cents per burrow. In 1912, Surgeon John D. Long 2 put the cost of the various methods of destruction, with carbon bisulphide at 90 cents per gallon, as follows; cost per acre, estimated on the basis of ten holes per acre. Carbon bisulphide, with "destructor" (two treatments) $ .20 Poisoned grain (four or five treatments) 35 Carbon bisulphide, waste-ball method (two treatments) 68 Surgeon Long reports that in actual practice one gallon of bisulphide would treat from 200 to 250 holes when used with the "destructor" and from 50 to 60 holes when used per the waste-ball method. i Merriam, C. II. U. S. Dept. Agric, Biological Survey, Circular no. 76, 1910. 2 Long, J. D. United States Public Health TCeports, vol. 27, no. 39, September 27, 1912. Crude carbon bisulphide is still quoted (August, 1917) at 90 cents a gallon, in live-gallon lots in San Francisco, but strychnine has advanced to $1.35 per ounce for the sulphate and $1.60 per ounce for the alkaloid form. Ammunition has nearly doubled in price, so that the present cost of the various methods of destroying ground squirrels is, on the average, considerably higher than Surgeon Long's estimate, which latter seems to be the best and most accurate thus far published on the subject, both as to the number of treatments required and as to the relative cost. (1) POISONING WITH STRYCHNINE Barley as a vehicle for the poison is usually more attractive to the ground squirrel than wheat. It is also less likely to be eaten by birds, stock and poultry. Hence barley should be used for this purpose instead of wheat. Care should always be taken not to leave more than a teaspoonful of poisoned grain in a place and it should never be left where poultry can pick it up. The alkaloid form of strychnine is only slightly soluble in water and is considered the best form to use in preparing poisoned barley for the reason that it is not so easily affected by fog and rain. When gathered and placed in the cheek-pouches by the ground squirrel, the strychnine-coated barley often gets in its deadly work before the animal has a chance to detect the bitter taste of the strychnine and reject the poisoned grain. Formula for Strychnine-coated Barley. — Following is the latest government formula 3 for preparing poisoned barley for California ground squirrels. Barley (clean grain) 16 quarts Strychnine (powdered alkaloid) 1 ounce Bicarbonate of soda (baking soda) 1 ounce Thin starch paste % pint Heavy corn sirup % pint Glycerin 1 tablespoonful Saccharin ] /io ounce Mix thoroughly 1 ounce of powdered strychnine (alkaloid) and 1 ounce of common baking soda. Sift this into % pint of thin, hot starch paste and stir to a smooth, creamy mass. (The starch paste is made by dissolving 1 heaping table- spoonful of dry gloss starch in a little cold water, which is then added to % pint of boiling water; boil and stir constantly until a clear, thin paste is formed.) Add % pint of heavy corn sirup and 1 tablespoonful of glycerin and stir thor- oughly. Add y 10 ounce of saccharin and stir thoroughly. Pour this mixture over 16 quarts of clean barley and mix well so that each grain is coated. Caution.-*-A\l containers of poison and all utensils used in the preparation of poisons should be kept PLAINLY LABELED and OUT OF BEACH of children, irresponsible persons, and live stock. 3 Circular letter issued by Bureau of Biological Survey, U. S. Dept. Agric. June, 1917. 8 Placing Poisoned Grain. — The poisoned barley should be well scattered over clean hard ground near the holes. Squirrel paths that lead along fences or to or from the dens are good places in which to scatter the grain. Poisoned grain will be largely wasted if dropped in thick grass or in dusty places. It will also often be covered up if left on the loose dirt at the entrance to the burrow. Poisoning Fresh Fruits and Grain. — Strychnine sulphate is freely soluble in fruit juices and these seem to conceal, to some degree at least, the bitterness of the strychnine. Some of the best results in the writer's experience in poisoning squirrels were secured with oranges cut in halves which were then sprinkled with powdered strychnine and left in paths of the squirrels. Watermelon rinds often prove very effective if cut into pieces as large as one's hand and poisoned by sprinkling with powdered strychnine. Green barley heads in the "dough" stage, with the beards clipped off, have been found very deadly if soaked for fifteen or twenty hours in a solution of one ounce of strychnine sulphate to a gallon of water. The solution should be brought to a boil and then allowed to cool before the barley is put in. It is wise to take every precaution in placing these baits so as to put them in protected places, such as rockpiles, where there is no chance for stock to reach them; and it is also advisable to thoroughly wash one's hands immediately after putting out the poisoned bait. (2) FUMIGATION WITH CAEBON BISULPHIDE Carbon bisulphide gas is one of the best agents for destroying those ground squirrels that have failed to take the poisoned grain or, having once survived the poison, refuse to take it again. The follow- ing facts should be kept in mind regarding the use of carbon bisul- phide, (a) The gas from carbon bisulphide is highly inflammable and it should be kept away from all fires and exposed lights. (b) Being heavier than air, this gas settles in the lowest places in the underground burrow and hence will not go over an elevation higher than the entrance of the burrow unless an "exterminator" or "de- structor" is used to forcibly pump the burrow full of gas or unless the gas is exploded in the burrow. (c) When the ground is dry and full of cracks the gas escapes and is not nearly as effective as if used when the ground is wet and the gas therefore confined to the burrow, (d) It should be used only in holes that are known to be occupied by squirrels at the time of the treatment, '(e) Carbon bisulphide should be kept tightly corked as it loses strength rapidly on exposure to the air. The two best methods of applying carbon bisulphide are by the use of the "waste-ball" method and of the "destructor." The com- mon waste-ball method is to pour a tablespoonful of carbon bisulphide on a piece of cotton waste, corncob, horse manure, or other absorptive material, which should then be thrown as far down the hole as possible and the opening immediately closed with earth. Exploding the Gas. — The explosion of the gas in connection with the waste-ball method is recommended where the ground is damp and there is no danger from fire. When the bisulphide gas in a burrow is exploded two new gases (carbon monoxide and sulphur dioxide) are formed, both poisonous. These diffuse somewhat more rapidly and pass more readily over elevations than bisulphide and penetrate to the very ends of all branches of the burrow. A "destructor" should be used in grain fields or in other places where there is danger from fire, since by its use the burrow is pumped completely full of the carbon bisulphide gas and hence the explosion of the gas becomes unnecessary. A six-foot piece of 14-inch pipe with one end closed and pointed and the other end tightly wrapped with a rag soaked in coal oil adds safety to the operation of exploding the gas in the burrow. After the bisulphide has been confined in the burrow for a few seconds, a hole is made with the pointed end of the pipe through the dirt plug at the entrance of the burrow. The gas is then "touched off" w T ith the torch, which has been previously lighted, on the other end of the rod. It is advisable to stand well to one side of the burrow when doing this. The second system of applying carbon bisulphide has been used by Passed Assistant Surgeon John D. Long of the U. S. Public Health Service, who devised a simple "destructor" which pumps the vapor- ized bisulphide into the burrow. 4 Laboratory experiments showed that the animal is but little alarmed by the gas and makes no effort to escape or to seek fresh air. In ten or fifteen minutes after the gas is pumped into the burrow the animal falls over and in from thirty to forty-five minutes is dead. This destructor (fig. 3) is composed principally of 18-gauge galvanized iron. The circular top, bottom and piston are made from veneered wood so as to prevent warping or splitting. Stated simply, the main parts of this apparatus are as follows: An air chamber (1), containing the piston (10), is entirely surrounded by the bisulphide tank (2). This tank is connected with the vaporizing chamber (4) through the measuring cup (15). In operating the destructor, a short rubber hose connected to the outlet (17) is inserted at least one foot into an occupied squirrel burrow and tightly surrounded with dirt. Then the three-way cock (16) * Long, J. D. United States Public Health Reports, vol. 27, no. 39, Septembei 27, i.912. 10 is turned so that the measuring cup (15) is filled with y 2 ounce of refined bisulphide, which is permitted by another turn of the cock to run into the vaporizing chamber (4). The pump has a double action, for air is admitted at the proper time at the inlet valves (7) at both the top and the bottom of the cylinder when the piston (10) is worked up and down by the handle (14). The air thus compressed escapes through the outlet valves (8) into the air shaft (9), which in turn conveys it to the vaporizing chamber (4). From the vaporizing chamber the bisulphide gas is forced into the burrow through a rubber hose connecting with the outlet (17). Fifteen double strokes of the pump forces 12 cubic feet of 1.5 per cent bisulphide gas down the squirrel burrow; this is sufficient to kill the animal. The rubber hose is then withdrawn from the burrow and the hole closed by stamping in the dirt with the heel of one's shoe. This destructor has been placed on the market through a San Francisco firm. The Eureka Squirrel Exterminator and other sim- ilar machines operate on principles similar to that of the destructor just described, while a rancher of mechanical turn of mind should be able to construct a machine for the most part out of an old brass cylinder and other materials from the scrap pile to be found about the average ranch. (3) TKAPPING; (4) SHOOTING Where ground squirrels are digging into ditch banks, and in similar cases where they must be disposed of promptly at any cost, special means of getting rid of them must be adopted. Trapping and shooting are two valuable methods of control for such local appli- cation. While these two methods can be used at any season, the time required to keep the traps properly set, which is essential to success, and the high initial cost of the traps as well as the present high cost of ammunition make them too expensive for general use on large acre- age. Trapping and shooting are worth while in cleaning up the few wise squirrels which escape the poison and carbon bisulphide, and in reducing the breeding stock in the early spring before the annual five-fold increase. The No. 1 Oneida jump trap is the best trap to use, as it is lighter, easier to set, and has a larger catching surface (pan or treadle) than the ordinary steel trap with the outside spring. The jump trap lies flat on the ground ; the jaws have wide contact surfaces which reduce the chance of breaking the animal's leg; and the construction of the inside spring causes the trap to jump up and take a high grip on the leg instead of on the foot only. Such traps may be set without bait in the entrances to the burrows, or, baited with rolled barley, set in the squirrel paths, or near the places where the squirrels are feeding. In any case it is well to scrape out by a shove of the foot a slight 11 Fig. 3. — Sectional view of squirrel "Destructor." (Drawing from blueprint furnished by United States Public Health Service.) 1, air cylinder; 2, bisulphide tank; 3, filler; 4, vaporizing chamber; 5, veneer wood circles; 6, air space to lower valves; 7, inlet air valves; 8, outlet air valves; 9, air shaft; 10, piston head; 11, piston rod; 12, lock nuts; 13, cup leather packing; 14, handle; 15, measuring cup; 16, three-way cock; 17, hose outlet; 18, air inlet to vaporizing chamber; 19, foot rest; 20, air vent in measuring cup; 21, air deflector; 22, bottom board. 12 depression in which to place the trap, so that when set, the upper surface of each trap will be flush with the surface of the surrounding ground. The traps should be well secured and this is conveniently done by passing a three-foot lath sharpened at one end through the ring in the end of the chain, and then driving the lath well into the ground. It will serve also as a marker, enabling one readily to find the trap. (5) ENCOURAGEMENT OF THE NATUEAL ENEMIES OF THE GROUND SQUIRREL The killing-off of the natural enemies of the ground squirrel de- stroys Nature's most effective check on these destructive rodents. Some of these age-long natural enemies of the squirrel are : coyotes, badgers, weasels and wildcats, among mammals; rattlesnakes and gopher snakes, among reptiles; red-tailed hawks and golden eagles, among birds. Badgers, weasels and snakes capture the ground squir- rels in their burrows. Wildcats and coyotes lie in wait near the burrows untij. the squirrels venture forth in search of food, when they pounce upon them. Hawks and eagles swoop down on the squirrels .from their vantage points in the air. The fact that there are so many and varied natural checks on the ground squirrel shows the necessity of preserving as many of these native enemies as possible, if the prolific squirrel is to be kept within bounds. The aid of coyotes, wildcats and rattlesnakes may well be dispensed with ; but badgers, gopher snakes, hawks and eagles cost us little or nothing to let alone ; and each one of these animals is catching ground squirrels almost throughout its lifetime. The following observations by James B. Dixon show what certain hawks and eagles actually accomplish in destroying ground squirrels. The dead squirrels counted in the nests cited represent merely the surplus which the old birds had carried to the young. The squirrels that the old birds or the young may have eaten on the day of observation are not taken into account. Destructive Rodents Found in Nests of Hawks and Golden Eagle in San Diego County Species of bird D ate Young- and eggs Locality Evidence Red-bellied Hawk Apr. 3 1916 3 young, 1 week old, and 1 rot- ten egg Pala 1 ground squirrel and 2 gophers Western Red-tailed Mar. 28, 1906 1 day-old chick, 2 Vista remains of 2 Hawk pipped eggs and 1 rotten egg ground squirrels Golden Eagle Mar. 26, 1909 1 day-old chick Rincon 9 jack rabbits Golden Eagle Apr. 4, 1907 2 young, 1 week old Lilac 1 1 ground squirrels in and about nest 13 OTHER METHODS OF CONTROL Many small deciduous orchards are to be found more or less isolated in foothill regions in different parts of the state. Squirrel depredations in such orchards can often be prevented by tacking smooth pieces of tin about the tree trunks. If the tinning is started about two feet above the ground and continued upwards for two or three feet it will usually keep the ground squirrels out of the trees unless there are drooping branches which they can climb. Seed corn has been protected from ground squirrels during germin- ation by being treated with coal tar. 5 Add one large spoonful of coal tar to a gallon of boiling water. When the mixture has cooled some- what the corn may be stirred in and allowed to remain several minutes without danger to germination. SOME DIFFICULTIES IN GROUND SQUIRREL CONTROL One of the most discouraging features in the work of ground squirrel control is the indifferent, "do-nothing," attitude of a few people in each locality who make just as little effort as the law allows, to rid their land of these pests. Many conscientious and progressive ranchers have justly demanded to know why they should continue to rid their fields of ground squirrels when previous experience has shown that, when cleaned up, these fields have been promptly restocked from the squirrel-infested lands of their negligent neighbors. Now that we have an adequate squirrel-eradication law, there should be less cause for complaint on this score. There is no question but that the most effective campaign against ground squirrels is one in which the whole community joins. Co- operation in this work is the only way in which all the ground can be covered, and co-operation is therefore essential to success. The cost of the war on ground squirrels can be materially reduced by a community purchasing strychnine and carbon bisulphide in wholesale quantities. One of the most successful co-operative efforts along this line in California was conducted as follows. A local ordinance com- pelling action in cleaning up infested land was secured. The squirrel inspector then worked in co-operation with the Farm Bureau, and barley and strychnine were purchased in quantities under the direc- tion of the Farm Advisor. The best known formula was used in making the poisoned grain, which was then packed in five-gallon wooden containers and shipped to central distributing points. Here it was sold at cost, which was at that time $2 per container. A copy 5 Lantz, D. E. U. S. Dept, Agric. Yearbook, Separate no. 708, 1916, p. 7. 14 of the formula used, with directions for administering an antidote for the poison, was pasted on the containers, together with the label ''Farm Bureau Squirrel Poison." This system insured a supply of uniform, effective, and reliable poisoned grain for the people's use at the lowest current price. BOUNTY SYSTEM A FAILURE Some variety of bounty system intended to secure the eradication of injurious rodents such as the ground squirrel has been tried, in Tulare and in other counties in California, but in most cases has proved far from satisfactory. Such a system usually results in an early depletion of the funds provided to pay the bounty, after which the animals are soon permitted to regain their former numbers. Bounties have not resulted in extermination of the animals aimed at in any of the several states where tried. A bounty high enough to secure extermination would be prohibitive on account of the cost, as no state or county could stand the financial strain for any great length of time. A lower bounty means that the animals will be trapped only so long as it is profitable, after which they will be left to breed up again. L. B. Nagler, Assistant Secretary of State in Wisconsin, says: "I have had ten years' experience in auditing bounty claims, and the results convince me that the system in vogue is not only ineffective, but wasteful, and, in a large measure, harmful. ' ' It is the opinion of those best informed on the subject, that the bounty system is not only vastly expensive and productive of endless fraud, but that it fails to accomplish the end desired. Fins, Feathers and Fur, June, 1917, p. 1. STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION REPORTS 1897. Resistant Vines, their Selection, Adaptation, and Grafting. Appendix to Viticultural Report for 1896. 1902. Report of the Agricultural Experiment Station for 1898-1901. 1903. Report of the Agricultural Experiment Station for 1901-03. 1904. Twenty-second Report of the Agricultural Experiment Station for 1903-04. 1914. Report of the College of Agriculture and the Agricultural Experiment Station, Julv, 1913-June, 1914. 1915. Report of the College of Agriculture and the Agricultural Experiment Station, Julv, 1914-June, 1915. 1916. Report of the College of Agriculture and the Agricultural Experiment Station, July, 1915-June, 1916. 1917. Report of the College of Agriculture and the Agricultural Experiment Station, July, 1916 — June, 1917. No. 230. 241. 242. 246. 248. 249. 250. 251. 252. 253. 255. 257. 261. 262. 263. 264. 265. 266. 267. 268. No. 113. 114. 115. 121. 124. 126. 127. 128. 129. 131. 133. 134. 135. 136. 137. 138. 139. 140. 141. 142. 143. 144. 145. 147. 148. 150. 151 BULLETINS No. Enological Investigations. 270. Vine Pruning in California, Part I. Humus in California Soils. Vine Pruning in California, Part II. 271. The Economic Value of Pacific Coast 272. Kelps. 273. Stock-Poisoning Plants of California. The Loquat. • 274. Utilization of the Nitrogen and Organic Matter in Septic and Imhoff Tank 275. Sludges. Deterioration of Lumber. 276. Irrigation and Soil Conditions in the 277. Sierra Nevada Foothills, California. 278. The Citricola Scale. 279. New Dosage Tables. 280. Melaxuma of the Walnut, "Juglans regia." 281. Citrus Diseases of Florida and Cuba Compared with Those of California. 282. Size Grade for Ripe Olives. The Calibration of the Leakage Meter. 283. Cotton Rot of Lemons in California. 284. A Spotting of Citrus Fmits Due to the 285. Action of Oil Liberated from the Rind. 286. Experiments with Stocks for Citrus. 287. Growing and Grafting Olive Seedlings. CIRCULARS Correspondence Courses in Agriculture. Increasing the Dutv of Water. Grafting Vinifera Vineyards. Some Things the Prospective Settler Should Know. Alfalfa Silage for Fattening Steers. Spraying for the Grape Leaf Hopper. House Fumigation. Insecticide Formulas. The Control of Citrus Insects. Spraying for Control of Walnut Aphis. Countv Farm Adviser. Control of Raisin Insects. Official Tests of Dairy Cows. Melilotus Indica. Wood Decay in Orchard Trees. The Silo in California Agriculture. The Generation of Hydrocyanic Acid Gas in Fumigation by Portable Ma- chines. The Practical Application of Improved Methods of Fermentation in Califor- nia Wineries during 1913 and 1914. Standard Insecticides and Fungicides versus Secret Preparations. Practical and Inexpensive Poultrv Ap- pliances. Control of Grasshoppers in Imperial Valley. Oidium or Powder'- Mildew of the Vine SuErcrostions to Poultrvmon concerning Chicken Pox. Tomato Growing in California. "Lnngworms." Round Worms in Poultrv. Feeding and Management of Hogs. No. 152. 153. 154. 155. 156. 157. 158. 160. 161. 162. 164. 165. 166. 167. 168. 169. 170. 171. Ml. 173. 174. 175. 177. 178. A Comparison of Annual Cropping, Bi- ennial Cropping, and Green Manures on the Yield of Wheat. Feeding Dairy Calves in California. Commercial Fertilizers. Preliminary Report on Kearney Vine- yard Experimental Drain. The Common Honey Bee as an Agent in Prune Pollination. The Cultivation of Belladonna in Cali- fornia. The Pomegranate. Sudan Grass. Grain Sorghums. Irrigation of Rice in California. Irrigation of Alfalfa in the Sacramento Valley. Control of the Pocket Gophers in Cali- fornia. Trials with California Silage Crops for Dairy Cows. The Olive Insects of California. Irrigation of Alfalfa in Imperial Valley. The Milch Goat in California. Commercial Fertilizers. Vinegar from Waste Fruits. Some Observations on the Bulk Hand- ling of Grain in California. Announcement of the California State Dairv Cow Competition, 1916-18. Irrigation Practice in Growing Small Fruits in California. Rovine Tuberculosis. How to Operate an Incubator. Control of the Pear Scab. Home and Farm Canning. Lettuce Growing in California. Potatoes in California. White Diarrhoea and Coccidiosis of Chicks. Small Fruit Culture in California. Fundamentals of Sugar Beet under California Conditions. The County Farm Bureau. Feeding Stuffs of Minor Importance. Spraying for the Control of Wild Morn ing-Glory within the Fog Belt. 1918 Grain Crop. Fertilizing California Soils for the 1918 Crop. Th^ Fertilization of Citrus. Wheat Culture. The Construction of the Wood-Hoop Silo. Farm Drainage Methods. Progress Report on the Marketing and Distribution of Milk. Hog Ohnlora Prevention and the Serum Treatment. Oraip Sorehnm Seed. The Packing of Apples in California.