White as a Ghost: Winter Ticks and Moose

Bill Samuel
Federation of Alberta Naturalists, Natural History Series,
Edmonton
November 2004; 97 pp.
Price: $31.00
ISBN: 0-9696134-6-6

 This book provides an overview of Dr. Samuel’s extensive and unique research on host/tick interactions between moose and the winter tick, Dermacentor albipictus. Heavy tick infestations cause moose to lose their outer hair and appear pale, thus leading to the moniker “ghost moose.” The production quality of this book is excellent, including numerous full-color photographs and diagrams. Although intended for a diverse audience, the author also made the book a resource for professional scientists by providing a complete list of primary citations.  Dr. Samuel’s gentle but not detracting humor is intertwined throughout the text. Perhaps predictably, many heading words normally ending in “tic” gain a terminal “k” from Dr. Samuel’s pen!

The book begins with a preface outlining the history of the author’s interest in parasites and tick–moose interactions. A narrative prologue follows, relating the engaging story of a moose bull calf, born in the spring and thriving until the following January, when intensive bouts of grooming began against the tick infestations acquired the previous autumn. The author describes, with genuine pathos but without sentimentality, the calf’s deterioration over the coming months and its demise in April. This story sets the stage for the rest of the book.

Chapter 1 describes the biology of the winter tick and moose in Canada. Chapter 2 offers an historical perspective, beginning with the first description of D. albipictus in 1869 and continuing with the growing impact of winter ticks on moose and other wildlife at three-decade intervals from the early 1900s to the present. The author retains the reader’s attention by interjecting interesting anecdotes among the scientific data.

The annual life cycle of the winter tick in Alberta is described in Chapter 3. This cycle is so predictable that, on at least one occasion, it was possible to prove in court, by the tick life stages present on the hide, that a moose had been killed by a poacher well after the hunting season. The behavioral characteristics of winter ticks that determine where female ticks oviposit and that enable questing larvae to sense and latch on to passing hosts from the clumps of vegetation are outlined in Chapter 4.  Dr. Samuel has included striking photographs of larval tick clumps questing on vegetation and larvae with interlocking legs that enable the entire string of larvae to transfer to the host after only one larva has made contact. 

In Chapter 5, the author describes his sampling methods for accurately determining distribution patterns and total tick burdens on wildlife hides. Although elk, white-tailed deer, and bison normally have relatively modest tick burdens (an average of 1,200 or fewer per animal in one study), 20% of moose were burdened with more than 50,000 per animal, with a few harboring more than 100,000! Chapter 6 outlines the considerable damage inflicted upon moose as a result of these heavy infestations. As the winter gives way to spring, and female ticks begin to engorge, moose spend less time feeding and more time grooming. This intense grooming activity results in anemia, loss of visceral fat and the winter coat hair, and retarded growth of young moose.

Chapter 7 describes the behavioral strategies used by moose to evade winter tick infestations. Moose are not efficient groomers, in part accounting for their much higher tick burdens reported in Chapter 5. However, reminiscent of oxpecker birds in Africa, various birds feed opportunistically on the winter ticks infesting moose. Chapter 8 describes the helminth parasites that moose also endure, including the meningeal worm, Parelaphostrongylus tenuis, and the large American liver fluke, Fascioloides magna. One of the main strengths of this book is the considerable detail devoted to describing the combined effects of these parasites on moose, as well as the evolution of host–parasite interactions.

Finally, in Chapter 9, Dr. Samuel proposes management strategies for controlling winter tick infestations. The importance of preserving moose populations is emphasized, focusing on the intrinsic beauty of the animals, their role in North America’s wildlife heritage and complex ecosystem, and their use as an important food source, particularly for some communities. In the Epilogue, he alludes to the role that responsible hunting might play as part of the overall management strategy for wild moose.

Projected blood loss due to tick infestations is described in the Appendix.  Cows and bulls must replace a minimum of 11% and 17% respectively of their blood volume, and calves, astonishingly, must replace a minimum of 58% of their blood volume during the late winter and early spring. Statistics such as these make one marvel at those moose that manage to survive heavy tick infestations.

In summary, this book is one of the most comprehensive studies of tick–host interactions in nature. The conduct of these studies serve as a model for the study of tick–host interactions worldwide. We highly recommend this fascinating book as an excellent supplemental resource for courses at all levels, especially considering its modest price.

Katherine M. Kocan
Center for Veterinary Health Sciences
Oklahoma State University
Stillwater, OK, 74078
E-mail: katherine.kocan@okstate.edu

W. Reuben Kaufman
Department of Biological Sciences
University of Alberta
Edmonton, Alberta
American Entomologist
Vol. 52, No.4, Winter 2006