BURROW-BUILDING STRATEGIES AND HABITAT USE OF VOLES IN PACIFIC NORTHWEST ORCHARDS

Seidel and Booth (1960) wrote that the "life histories of the genus Microtus are not numerous in the literature." In support of his observation he cited 6 publications, all dated between 1891 and 1953. Since then the literature has exploded with a proliferation of publications. An international literature review recently revealed over 3,500 citations for the genus. When Pitymys and Clethrionomys are included another 350 and 1,880, respectively, were found. Over the last 10 years approximately 3 new publications on voles appeared every 4 days; a significant output for what some would consider such an insignificant species. Most of the publications were the result of graduate research projects on population dynamics and species ecology. As such, many do not explore more than the rudimentary ecological relationships between the animal and their environments. Unfortunate, as well, is that all but one confined their observations to only a small part of their total environment. For many of these animals, their life underground may be more important for their survival than that above ground. Trapping studies conducted by Godfrey and Askham (1988) with permanently placed pitfall live traps in orchards revealed a significant inverse population fluctuation during the year. During the winter, when populations are expected to decrease, as many as 6 to 8 mature Microtus montanus were collected at any 1 time in the traps after several centimeters of snow accumulation. During the summer, when populations are expected to increase, virtually no animals were collected in the traps. According to current population dynamics theory, greater numbers of animals, including increasingly larger numbers of immature members of the community, should appear in any sample between the onset of the breeding period, generally in the spring, taper off during the latter part of the production season, usually late summer, and then decline as the limiting factors begin to take effect. For us, we trapped more animals in the fall and early winter than we did during the spring and summer. A review of the above literature did little to answer our question. Where are the animals going during the summer and why?

RELATED LAWS ON EXOTIC AND NATIVE WILD ANIMALS

This paper is submitted in an effort to acquaint the personnel of allied State agencies with related laws which control the public and private possession of live exotic and native wild animals. The need for this common knowledge of related laws by agencies with law enforcement responsibility is readily apparent when the annual number and related problems from imported or resident wild animals in California are examined. In addition to resident wild animal populations, millions of fish and thousands of mammals, birds, and reptiles enter California each year through the utilization of most methods of transportation. Most of these imported animals are exotic species from foreign lands which cannot be readily identified and pose various degrees of potential and actual threat to native wild life, agriculture, and public health if they are introduced into the wilds of this State. For the purpose of this report, a general picture of imported exotic animals is presented in an introduction, and specific animals with related laws are treated individu-ally under the headings of current laws and future regulations.

HAWAIIAN SUGAR CANE RAT CONTROL METHODS AND PROBLEMS

The problem of rats in our Hawaiian sugar cane fields has been with us for a long time. Early records tell of heavy damage at various times on all the islands where sugar cane is grown. Many methods were tried to control these rats. Trapping was once used as a control measure, a bounty was used for a time, gangs of dogs were trained to catch the rats as the cane was harvested. Many kinds of baits and poisons were used. All of these methods were of some value as long as labor was cheap. Our present day problem started when the labor costs started up and the sugar industry shifted to long cropping. Until World War II cane was an annual crop. After the war it was shifted to a two year crop, three years in some places. Depending on variety, location, and soil we raise 90 to 130 tons of sugar cane per acre, which produces 7 to 15 tons of sugar per acre for a two year crop. This sugar brings about $135 dollars per ton. This tonnage of cane is a thick tangle of vegetation. The cane grows erect for almost a year, as it continues to grow it bends over at the base. This allows the stalk to rest on the ground or on other stalks of cane as it continues to grow. These stalks form a tangled mat of stalks and dead leaves that may be two feet thick at the time of harvest. At the same time the leafy growing portion of the stalk will be sticking up out of the mat of cane ten feet in the air. Some of these individual stalks may be 30 feet long and still growing at the time of harvest. All this makes it very hard to get through a cane field as it is one long, prolonged stumble over and through the cane. It is in this mat of cane that our three species of rats live. Two species are familiar to most people in the pest control field. Rattus norvegicus and Rattus rattus. In the latter species we include both the black rat and the alexandrine rats, their habits seem to be the same in Hawaii. Our third rat is the Polynesian rat, Rattus exlans, locally called the Hawaiian rat. This is a small rat, the average length head to tip of tail is nine inches and the average body weight is 65 grams. It has dark brownish fur like the alexandrine rats, and a grey belly. It is found in Indonesia, on most of the islands of Oceania and in New Zealand. All three rats live in our cane fields and the brushy and forested portions of our islands. The norway and alexandrine rats are found in and around the villages and farms, the Polynesian rat is only found in the fields and waste areas. The actual amount of damage done by rats is small, but destruction they cause is large. The rats gnaw through the rind of the cane stalk and eat the soft juicy and sweet tissues inside. They will hollow out one to several nodes per stalk attacked. The effect to the cane stalk is like ringing a tree. After this attack the stalk above the chewed portion usually dies, and sometimes the lower portion too. If the rat does not eat through the stalk the cane stalk could go on living and producing sugar at a reduced rate. Generally an injured stalk does not last long. Disease and souring organisms get in the injury and kill the stalk. And if this isn't enough, some insects are attracted to the injured stalk and will sometimes bore in and kill it. An injured stalk of cane doesn't have much of a chance. A rat may only gnaw out six inches of a 30 foot stalk and the whole stalk will die. If the rat only destroyed what he ate we could ignore them but they cause the death of too much cane. This dead, dying, and souring cane cause several direct and indirect tosses. First we lose the sugar that the cane would have produced. We harvest all of our cane mechanically so we haul the dead and souring cane to the mill where we have to grind it with our good cane and the bad cane reduces the purity of the sugar juices we squeeze from the cane. Rats reduce our income and run up our overhead.

HIGHLIGHTS OF BIRD CONTROL RESEARCH IN ENGLAND, FRANCE, HOLLAND, AND GERMANY

The purpose of this paper is to present a brief review of the research being conducted in England, France, Germany, and The Netherlands on problems caused by nuisance and depredating birds. Much of the information presented has been obtained through correspondence with collaborators. In the fall of 1962, I discussed depredating bird and bird-airport problems with research workers in these countries, and also attended the meeting of the International Union of Applied Ornithology held in Frankfurt/Main. In November 1963, I attended an international symposium about the bird-airport problem, held in Nice, France. This paper will draw attention to the current research which I think will interest American investigators, but will not report every aspect of the foreign investigations. Details appear in the publications that are listed.

THE INFLUENCE OF ATTRACTANTS AND REPELLENTS ON THE FEEDING BEHAVIOUR OF Rattus norvegicus

Poison baits are extensively used for commensal rodent control; considerable folk lore exists regarding the use of additives to induce rodents to come to and eat poison baits. This paper describes a rational evaluation of attractants and the influence of different odours in inducing Rattus norvegicus to feed at given locations. The influence of certain repellents was also examined. Tests consisted of attempts to induce rats to feed at non-preferred sites or to repel them from preferred sites. Place preference was the dominant factor in feeding by rats, and odours failed to influence feeding activity significantly.

METHODS OF CONTROLLING STARLINGS AND BLACKBIRDS

Most people have accepted the fact that all living things can be beneficial to mankind in some way or other. This is especially true of our wild birds, since they provide enjoyment and wholesome recreation for most of us, regardless of whether we live on farms or in the city. But despite the fact that wild birds are for the most part beneficial, at times individuals or populations of certain species can seriously affect man's interests. When such situations occur, some measures of relief are desirable and usually eagerly sought. This report is not intended to answer all the questions that may arise concerning problems with blackbirds and starlings; instead, it is merely a summary of measures used to protect agricultural crops from these birds.

ANIMAL POPULATION ECOLOGY AND CONTROL FUNDAMENTALS

Expensive, extensive and apparently lethal control measures have been applied against many species of pest vertebrates and invertebrates for decades. In spite of this, few pests have been annihilated, and in many cases the stated goals have become progressively more modest, so that now we speak of saving foliage or a crop, rather than extermination. It is of interest to examine the reasons why animals are so difficult to exterminate, because this matter, of course, has implications for the type of control policy we pursue in the future. Also, it has implications for the problem of evaluating comparatively various resource management strategies. There are many biological mechanisms which could, in principle, enhance the performance of an animal population after control measures have been applied against it. These are of four main types: genetic, physiological, populationa1, and environmental. We are all familiar with the fact that in applying a control measure, we are, from the pest's point of view, applying intense selection pressure in favor of those individuals that may be preadapted to withstand the type of control being used. The well-known book by Brown (1958) documents, for invertebrates, a tremendous number of such cases. Presumably, vertebrates can show the same responses. Not quite so familiar is the evidence that sub-lethal doses of a lethal chemical may have a physiologically stimulating effect on population performance of the few individuals that happen to survive (Kuenen, 1958). With further research, we may find that this phenomenon occurs throughout the animal kingdom. Still less widely recognized is the fact that pest control elicits a populational homeostatic mechanism, as well as genetic and physiological homeostatic mechanisms. Many ecologists, such as Odum and Allee (1950, Slobodkin (1955), Klomp (1962) and the present author (1961, 1963) have pointed out that the curve for generation survival, or the curve for trend index as a function of last generations density is of great importance in population dynamics.

Refuge Update – May/June 2009, Volume 6, Number 3

Table of Contents: Recovering the New England Cottontail FOCUS..Ready for Tomorrow Build It and They Will Come CARE: Restoring America’s Wildlife Refuges

Refuge Update – May/June 2008, Volume 5, Number 3

Table of Contents: Liberating Rat Island, page 4 Focus on . . . Through the Eyes of Children, pages 10-19 Back to Midway, page 23

Refuge Update – May/June 2005, Volume 2, Number 3

Table of Contents: Friends Flourish, page 3 Yukon Delta Refuge Hosts Major Shorebird Research, pages 4-5 Focus on…Nature Photography, pages 8-14 Learning a New Language, pages 18-19

Refuge Update – May/June 2004, Volume 1, Number 3

Table of Contents: Recreation Fees Change the Face of Refuges, page 4 Focus on Cultural Resources, page 8 “Ambassadorship” is Thriving in Texas, page 15 BayScaping: Conserving Views and Habitats, page 16

Refuge Update – March/April 2008, Volume 5, Number 2

Table of Contents: Crystal River’s Manatee Rescue Squad, page 3 Focus on . . . Birds and Birding, pages 8-15 Assessing Damage in an Arizona Wilderness, page 16 Have Hammers, Will Travel page 18

Refuge Update – March/April 2009, Volume 6, Number 2

Table of Contents: America’s Birds: In an Alarming State Snakes Alive! Title Sub Title East Coast Wetlands Are Disappearing Chief’s Corner: What We Do Now Extreme Makeover for Bird Sightings by Mike Carlo Taking Care of Our World War II Legacy by Lisa Matlock Whatever Happened to . . . . San Francisco Bay Wetland Restoration Projects Recalling the Battle of Long Island Sound by David Klinger Bold Approaches for Climate Change How Alligator River Refuge Is Planning and Adapting by Mike Bryant Rapid Climate Change Is Transforming the Arctic by David Payer Tracking Change on Wildlife Refuges by Kathy Granillo Where SLAMM Foretells a Wetter Future Reviving the Land – and the Air by Bob Ford and Pete Jerome Connecting the Conservation Landscape a New Priority by Mike Scott and Bob Adamcik Awards for Refuge System Palmyra Atoll Refuge Becomes Ramsar Site Not So Strategic Habitat Conservation: A True Story by David Viker Putting Food on Alaskan Tables by Andy Aderman

Refuge Update – March/April 2006, Volume 3, Number 2

Table of Contents: Energy Company Fine Benefits Ottawa Refuge, page 3 Hide and Seek…but Mostly Hide page 4 Focus on …Pollinators, page 10 Great Storytellers, page 18

Refuge Update – March/April 2007, Volume 4, Number 2

Table of Contents: What’s Melting: Togiak Refuge Sizes Up Its Glaciers, page 3 Focus on Fish Conservation, pages 10-15 Whatever happened to…, pages 16-17 Wildlife Cooperatives, page 20