UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA CIRCULAR 296 Eevised May, 1925 September, 1925 CONTROL OF THE CALIFORNIA GROUND SQUIRREL JOSEPH DIXON (Contribution from the Museum of Vertebrate Zoology of the University of California) Fig. 1. — Diagram showing methods of destroying ground squirrels to be employed at different seasons of the year. The ground squirrels are undoubtedly the most widely known and at the same time among the most destructive mammals in California. The large, long-tailed, grayish-brown species known as the California or "digger" squirrel (Citellus beecheyi and subspecies) is the most important in relation to man; first, because of its destructiveness to 2 UNIVERSITY OP CALIFORNIA — EXPERIMENT STATION 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 Califor- nia and the coast district south from the Golden Gate clear to the Mexican line ; and the gray-toned Fisher ground squirrel whose habitat lies in the southern San Joaquin and Owens valleys and south along the western border of the Mohave Desert. The characters which serve to distinguish these different races are not of any particular significance in relation to the work of eradication, so that from this standpoint the three forms may be considered as one. A knowledge of certain habits of feeding, breeding and hibernation, however, possessed in common by these animals is of the greatest importance in control work and these habits are considered at some length in the following pages. NATURE AND EXTENT OF DAMAGE In 1920, Mr. F. E. Garlough, of the United States Biological Survey, placed the average annual loss due to ground squirrels in California at twelve million dollars. Allowing for the decline in prices since 1920, it is the author's opinion that the annual loss due to ground squirrels in this state is now 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. Many kinds of fruit and practically all kinds of grain 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 one thousand plague-infected ground squirrels were examined from a single county in the San Francisco Bay region by the United States Public Health Service. That the immediate danger of acquiring the plague through ground squirrels has not passed, is shown by the virulent outbreaks of the disease in Alameda County in 1918 and in Los Angeles County in 1924. Their destruction in the infected districts would tend to diminish the frequency of recurrence of this danger. ClRC. 296] CONTROL OF THE CALIFORNIA GROUND SQUIRREL FEEDING HABITS California ground squirrels have membranous cheek-pouches which open inside the mouth and which are used to carry food, principally grain, to the underground storerooms. 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. 1 During the rainy season, from November to April, although they eat some grain, seeds or nuts that have been stored during the previous summer, their main food is grass and other green herbage. This results in serious loss in many locali- ties, by reducing greatly the pasturage available for horses and cattle. By weighing the food eaten by squirrels, I have found that 200 ground squirrels on the open range consume as much green forage as one steer, and 20 as much as one sheep. When green stuff is abundant, comparatively 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 extensively 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. i For a detailed account of general habits, see: Grinnell, J., and Dixon, J. Natural history of the ground squirrels of California. Mo. Bull. State Comm. Hort. (Sacramento), 7, nos. 11-12, 597-708, plates 5, 1918. UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION AESTIVATION OF THE GROUND SQUIRREL There is evidence that a period of aestivation, or torpidity induced by the dryness and accompanying food shortage in summer, obtains among some of the adult ground squirrels in the valleys of California. This period may extend continuously from late summer well through midwinter, and thus involve hibernation as well as aestivation. Only the old adults seem to "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 female ground squirrel that lived under normal conditions in a dooryard was kept under regular and continual observation. This 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. When removed from the burrow during this period, it was found to be in a torpid state and respiration was not perceptible. It emerged in an emaciated condition, with marked regularity, about the 22nd of each following February. This habit of aestivation affords explanation of a case in my 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 field the following February. This 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 exceedingly difficult to follow any individual squirrel through all its various activities for any great length of time. However, it suggests the advisability 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 ques- tion, too, whether or not a dormant animal, in which respiration is extremely slow, would be fatally injured by fumigation before the gas disappeared. TIME AND RATE OF BREEDING The accompanying chart (fig. 2), based on over 10,000 female squirrels examined by the United States Public Health Service during the spring and summer of 1910, shows that the California ground squirrel has a very definite breeding season which 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. Most of the young are born about five weeks after this CIRC. 296] CONTROL OF THE CALIFORNIA GROUND SQUIRREL 5 date and may be seen running about at the entrances of the burrows when a month or six weeks old. In low, warm valleys the breeding season has been found to be somewhat earlier, 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. The average number of embryos in pregnant females was found by the United States Public Health Service to be 7.2. W. C. Jacobsen 2 found that on areas where control Jan. Feb. Mar. Apr. MaY 10 3d 36 34 32 30 2b 26 24 22 20 18 16 14 IZ 10 8 6 4 2 22 29 5 •iSL l& 26 J 12 /9 26 Z 9 16 23 00 7 14 __| L } \ 1 I / \ 1 \ / i \ 1 \ i \ r \ ~T V \ I \ j \ i \ / ^ '- •v^ f i **■ H^ ' i k - \ s S^ \ ! / / \ / / \ \ / / \ i r / \ \ / / \ ! J / t / Fig. 2. — Chart showing breeding season of California ground squirrels. (Com- piled chiefly from data obtained from United States Public Health Reports, vol. 27, July 5, 1917, p. 1070.) Figures in left-hand column represent per cent of females found pregnant; over 10,000 females examined. ■ represents prevalence of pregnancy 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. operations had been carried on for two years or longer, and where the food supply had increased by the diminution of the number of squirrels, the litters were uniformly larger than where the work of reducing the squirrel population had just begun. Thus in Tulare County, where ground squirrels had been greatly reduced in numbers for a period of years, Jacobsen found that 86 pregnant females con- tained 846 embryos, an average of nearly 10 per litter. There is 2 Jacobson, W. C. Rate of reproduction in Citellus oeecheyi. Journal of Mamm., 4, 58, 1923. 6 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION some evidence that a second litter ia sometimes raised in a single season, but this is certainly not usual. The important point 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 destruction 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 literally "save nine." METHODS OF CONTROL The five most effective methods of destroying ground squirrels are : (1) poisoning with strychnine; (2) fumigation with carbon bisulfide or cyanide; (3) trapping; (4) shooting; (5) encouragement of the natural enemies of the ground squirrel. WHICH METHOD TO USE, WHEN, AND WHY (See Fig. 1) 1. 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. It has been found by Mr. Garlough that where ground squirrels are eating green alfilaria in quantity, poison grain though eaten has little or no effect. This is explained by the fact that this plant contains enough tannin, which is an antidote for strychnine, to neutralize the poison. In certain localities acorns are said to have a similar effect. 2. Powdered strychnine (sulfate) in fresh vegetables and fruit is especially effective in the dry season when green food is scarce. 3. Carbon bisulfide or cyanide is most effective when the soil is damp. When the ground is dry the gas escapes through the cracks in the soil. 4. 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. 5. Reel-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 merely allowed to live. It costs little to let them alone, to go about their business in the natural wav. ClRC. 296] CONTROL OF THE CALIFORNIA GROUND SQUIRREL COMPARATIVE COST OF VARIOUS METHODS In 1910, Dr. C. Hart Merriam 3 gave the cost of one treatment with poisoned grain as 3 cents per acre and for one treatment with carbon bisulfide ("waste-ball"" method) at 1% cents per burrow. In 1912, Surgeon John D. Long 4 puts the cost of the various methods of destruction, with carbon bisulfide at 90 cents per gallon, as follows ; cost per acre, estimated on the basis of ten holes per acre. Carbon bisulfide, with "destructor" (two treatments) $ .20 Poisoned grain (four or rive treatments) 35 Carbon bisulfide, waste-ball method (two treatments) 68 Surgeon Long reports that in actual practice one gallon of bisulfide would treat from 200 to 250 holes when used with the "destructor" and from 50 to 60 holes when used with the waste-ball method. Crude carbon bisulfide is quoted (April, 1925) at $1.15 per gallon, in five-gallon lots in San Francisco. Strychnine is quoted from 78 cents to 93 cents per ounce for the sulfate, and from $1.00 to $1.19 per ounce for the alkaloid form, according to the quantity purchased. The price of ammunition is also high, 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 STEYCHNINE 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. It should therefore 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 s Merriam, C. H. U. S. Dept. Agric, Biological Survey, Cir. 76:1910. 4 Long, J. D. United States Public Health Eeports, 27, no. 39, September 27, 1912. 8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 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. — The following is the regular government formula 5 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 ^4 pint Glycerin 1 tablespoonful Saccharin y 10 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 y± 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. — All 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 livestock. 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 sulfate 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 the paths of the squirrels. Watermelon rinds, if cut into pieces as large as one's hand and poisoned by sprinkling with powdered strychnine, often prove very effective. It is wise to take every pre- caution to place these baits in protected places, such as rockpiles, where there is no chance for stock to reach them ; and it is also advisable thoroughly to wash one's hands immediately after putting out the poisoned bait. 5 Circular letter issued by Bureau of Biological Survey, U. S. Dept. Agric, June, 1917. ClRC. 296] CONTROL OF THE CALIFORNIA GROUND SQUIRREL (2) FUMIGATION WITH CARBON BISULFIDE OR CYANIDE Carbon bisulfide 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 following facts should be kept in mind regarding the use of carbon bisulfide. (a) The gas from carbon bisulfide 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 ' ' destructor ' ' is used forcibly to 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, therefore, not nearly so effective as if used when the ground is wet and the gas thus 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 bisulfide are by the use of the "waste-ball" method and of the "destructor." The common waste-ball method is to pour a tablespoonful of carbon bisulfide 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. 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 bisulfide gas and the explosion of the gas is unnecessary. A six-foot piece of %-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 bisulfide 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" with 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 bisulfide 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 10 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION vaporized bisulfide into the burrow. 6 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 pre- vent warping or splitting. The main parts of this apparatus are as follows: An air chamber (1), containing the piston (10), is entirely surrounded by the bisulfide 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) is turned so that the measuring cup (15) is filled with y 2 ounce of refined bisulfide, 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 bisulfide 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 bisulfide 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. This destructor has been placed on the market through a San Francisco firm. The Eureka Squirrel Exterminator and other similar 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. The present high cost of farm labor favors the use of the ''waste-ball" rather than the ''destructor." Cyanide in the form of flakes, coarse powder, or dust which liberates the poisonous hydrocyanic acid gas has recently been placed on the market for use in gassing ground squirrels. From 1 to 2 ounces per burrow is used. The material should be placed down in the hole as far as possible, with a long-handled spoon. The burrow should then be stuffed with grass or a newspaper and covered with earth. Care must be exercised by the operator not to breathe the poison gas. This material can be had in 65-pound cans at from 18 to 23 cents a pound. e Long, J. D. United States Public Health Reports, 27, no. 39, September 27, 1912. ClRC. 296] CONTROL OF THE CALIFORNIA GROUND SQUIRREL 11 Fig. 3. — Sectional view of squirrel "Destructor." (Drawing from blueprint furnished by United State Public Health Service.) 1, air cylinder; 2, bisulfide 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 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Some ranchers report that they find it easier to use cyanide flakes than carbon bisulfide and that the percentage of squirrels killed is nearly or quite as good. In orchards cyanide is preferable to carbon bisulfide. However, in a series of tests reported early in 1925 by Mr. F. E. Garlough, of the United States Biological Survey, carbon bisulfide was found still to be the cheapest and best fumigant for general use in killing ground squirrels. (3) TRAPPING; (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 acreage. Trapping and shooting are useful in cleaning up the few wise squirrels which escape the poison and carbon bisulfide, and in reducing the breeding stock in the early spring before the annual five-fold increase. The No. 91 Oneida jump trap is the best, 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 depression in which to place the trap, so that when set, the upper surface will be flush with the surface of the surrounding ground. The traps should be well secured. 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. CIRC. 296] CONTROL OF THE CALIFORNIA GROUND SQUIRREL 13 (5) ENCOUKAGEMENT OF THE NATURAL ENEMIES OF THE GROUND SQUIRREL The killing-off of the natural enemies of the ground squirrel removes 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 squirrels in their burrows. Wildcats and coyotes lie in wait near the burrows until the squirrels venture forth in search of food, when they pounce upon them. Out of 186 stomachs of wildcats which have recently been examined from forty different localities in California, 26 contained ground squirrels, 21 held wood rats, 13 contained gopher remains, and 7 held mice. In this study rodents were found to con- stitute more than half of the food of wildcats. Hawks and eagles swoop down on the squirrels from their vantage points in the air. The value of preserving as many as possible of these native enemies of the ground squirrel is evident if this prolific animal is to be kept within bounds. The aid of coyotes and rattlesnakes may be dearly bought ; but badgers, gopher snakes, hawks and eagles cost us little or nothing, 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. Hawks and eagles it thus appears capture, when prey is abundant, far more than they and their young can actually consume. Destructive Rodents Found in Nests of Hawks and Golden Eagle in San Diego County Species of bird Date 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 Hawk Mar. 28, 1906 1 day-old chick, 2 pipped eggs and 1 rotten egg Vista Remains of 2 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 11 ground squirrels in and about nest 14 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 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 germination by being treated with coal tar. 7 Add one large spoonful of coal tar to a gallon of boiling water. When the mixture has cooled somewhat 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 asked 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. Cooper- ation in this work is the only way in which all the ground can be covered, and cooperation is therefore essential to success. The cost of the war on ground squirrels to a community can be materially reduced by purchasing strychnine and carbon bisulfide in wholesale quantities and mixing its own poisoned grain under the supervision of the Rodent Control Division of the State Department of Agriculture. This will insure a supply of uniform, effective, and reliable poisoned grain for each user at the lowest current price. 7 Lantz, D. E. U. S. Dept. Agric. Yearbook, Separate no. 708, p. 7, 1916. CIRC. 296] CONTROL OF THE CALIFORNIA GROUND SQUIRREL 15 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 it has proved far from satisfactory. Such a system usually results in an early depletion of the funds provided to pay the bounty. When this occurs 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: 8 "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 wastef ul 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. s Fins, Feathers and Fur, June, 1917, p. 1. 20m-9,'25