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Southern Africa
An invitation
After the publication of the Lewis and Narins 1985 Science paper (‘Do frogs communicate with seismic signals?’), I received a telephone call from Jim Reichman at Kansas State University (now at UC Santa Barbara) inviting me to join him in Cape Town to work on a project with his colleague, Jennifer Jarvis. He suspected that the Cape molerat was communicating with seismic signals in its territorial interactions— the animal lives in burrows and is fiercely territorial. I suggested that Peter Narins join us. Jim agreed, and I called Peter to let him know about the project. The Lewis-Lab would provide the necessary field equipment-- geophones, low-noise preamplifiers, thumpers, field (FM) tape recorder, field oscilloscope, and the like. The project was planned for early July, 1987.
Ned will join us
In June, 1987, Ned Lewis would be completing his Peace-Corps assignment in Tanzania. Having calibrated our geophones and being thoroughly familiar with the difficulties in coupling them securely to ground motion, and having tested and used all of the Lewis-Lab field gear in the field, Ned would be an ideal addition to the team. It was agreed that he should join us. South Africa was still embroiled in Apartheid, so Ned at first was reluctant to participate in the project. His African friends in Dar es Salaam convinced him that he should not miss the opportunity to visit Cape Town.
Visa problems
I met Ned in Arusha, about three weeks before the planned rendezvous in Cape Town. We visited Kibo and the Serengeti and environs and then spent a few days in Dar es Salaam while he finished his Peace-Corps paperwork. Next we flew to Harare for his visa and a visit to Victoria Falls and Hwange National Park. As the Trade-Mission staff contemplated Ned’s application, the Harare visit stretched beyond the rendezvous date. This required renewal of our Zimbabwe visitor’s visas, but gave us extra time for birding and sight-seeing in the eastern highlands. Finally we were told that the visa application would have to be sent to Pretoria for a decision. That process was going to take many weeks. Knowing that Peter was familiar with the field gear, I wired Jenny and told her that Ned and I would head home. As I knew it would be, the Narins, Reichman, Jarvis team was successful. I was not needed.
By the time the project was completed, in late July, our reliable international shipper had stopped doing business in South Africa. Getting the Lewis-Lab field gear home was another adventure.
My next trip to Africa was in 1993. Peter had applied for a Guggenheim fellowship to look for other animals using seismic signals. It had been awarded and he invited me to join him for a six-week trip in the fall. Three weeks would be spent in Madagascar, three in southern Africa. In Ranomafana National Park, Madagascar we would look for thumping frogs; in the Namib Desert we would look for evidence that the Namib golden mole was using seismic signals for prey location and navigation.
Madagascar interlude
In Madagascar we spent one week on logistics and permit gathering and two weeks in the field at the newly-established Ranomafana National Park. The Institute for Conservation of Tropical Environments provided a car and driver for the journey from Antananarivo to Ranomafana. Our campsite was 4 km from the road, near a clear stream that was free of schistosomes (one could bathe in it). Each morning a large troop of diademed sifakas passed through the canopy over our tents, and each afternoon a mixed flock of forest birds visited our campsite. Meals and boiled water were provided at a primitive field station about one hundred meters from our tents. We spent the first three nights evaluating calling frogs near our campsite. We needed a species that called from the ground and could be found reliably. None met these criteria.
A vociferous frog
On the fourth night we carried what field gear we needed up to the road and, with the aid of our car and driver, expanded our search. As we traveled slowly along the road, Peter listened from the left-rear window; I listened from the right front window. When we rounded a bend a few kilometers from our trailhead, I heard a chorus of frogs in the ditch next to the road. I got out of the car to get a closer look. As I was looking down at them with my headlamp, realizing that they undoubtedly were not suitable subjects for our project, I suddenly heard a strong frog vocalization at about eye level, then another and another. When I mimicked the call, I immediately got responses from several more frogs. As I walked along the ditch, ignoring the hundreds of tiny frogs calling there, I could easily see the much larger frogs at eye level and I could hear the amazing repertoire of calls they produced. This would be our animal subject—Boophis madagascariensis. There would be no seismic signals here, just the largest calling repertoire yet reported for a single species of frog (Narins et al., 2000, J Zool Lond 250 281-298). After the microphone and field tape recorder, the most valuable piece of equipment in this study proved to be the digital recorder designed for the Lewis Lab by Greg Kovacs. We used it to decompose recorded calls and reconstruct new versions for our playback experiments.
On to Gobabeb
Flying out of Madagascar required us to go through Nairobi, where we spent two nights, laundered our clothes, spent a day in Nairobi National Park, and ransomed our Madagascar field gear from the Nairobi ground crew of American Airlines. On the way to Antananarivo we had cached the rest of our field gear in large lockers at Johannesburg Airport. We recovered this en route from Nairobi to Windhoek, where we were met by Jenny Jarvis, her friend Rose Lee and her student Justin O’Riain. Jenny had a Cape Town University van to transport us all to Gobabeb, on the edge of the great linear dunes of the Namib Desert. Our study site was a few kilometers from the Gobabeb field station. To reach it, we drove largely on the sand— taking only short, well-delineated tracks across the gravel plains between dunes. This would minimize our lasting impact on the desert.
Foraging by the blind mole is not random
While Jenny, Rose and Justin mapped golden-mole foraging paths across the sand, Peter and I used the Lewis-Lab geophones and thumpers to explore the seismic world of the Namib. This included recording the footfalls of Tenebrionid beetles and palmatogeckos in the sand. The Namib golden mole lives on the lower edges of the giant dunes, not far from the neighboring gravel plains. Its preferred food is a solitary termite, which tends to be found munching on the roots of the dune grass. The dune grass tends to grow in isolated clumps, usually spaced five to ten meters apart. As it forages, the mole travels in nearly straight paths from one clump to another. On our study site, after leaving one clump, each mole seemed invariably to reach the next clump on its route well within 30 meters. The golden mole is sightless, making one wonder how it might sense the presence of grass clumps. The prevailing hypothesis was random foraging and chance encounter with each clump. To us, the foraging paths did not look random. With our seismic exploring, Peter and I already had learned that the grass clumps emitted vibrations—probably owing to the ever-present light wind blowing through the grass stubble above the surface of the sand. They might serve as seismic beacons for the moles. It seemed to me that before we could put that hypothesis forward, we needed to refute the random-foraging hypothesis. To do that, I suggested that we estimate the probability that a randomly selected straight path from each of the visited clumps would intersect a candidate successor clump within 30 meters. In every case, the probability of missing all clumps within 30 meters was much greater than the probability of intersecting one or more of them. The cumulative probability of randomly intersecting clump after clump over the 1400-meter average golden-mole foraging route each night was infinitesimal. Foraging was purposeful and must be guided by one or more senses—but not vision.
Completing the job
Although he continued to study the golden-mole—largely through his post-doc Matt Mason, it would be several years before Peter would be able to return with me to the Namib-- to demonstrate that at least one of those senses was seismic. In 2002 we did it—with a greatly expanded set of Lewis-Lab field gear (see Lewis et al, 2006). We were joined by Jenny and by Gary Bronner (Cape Town University) and Matt, who now was on the faculty at Cambridge. Jenny arranged for our study site—a Farmstead in the Namib Rand Nature Reserve, and, with the help of a large Cape Town University van and a trailer, handled the logistics on the ground. This included a post-study tour of southern Namibia, the western Kalahari, and the North Cape Province—complete with a massive wildflower bloom and blue cranes. Peter continues his golden mole studies today, and seismic communication is one of the current themes of his laboratory.
PM Narins et al., 1992, Seismic signal transmission between burrows of the Cape mole-rat, Georhychus capensis, J Comp Physiol A 170: 13-21.
PM Narins and ER Lewis, 1996, Extended call repertoire of a Madagascar frog, Biogeographie de Madagascar 1996:403-410.
Because Tanzania was one of the front-line nations (against Apartheid), with no South African consulate or trade mission, Ned would not be able to obtain a South-African entry visa there. Furthermore, he was traveling on a State-Department passport. I called the South African consulate in New York and was assured that neither of these things would be a problem, that Ned could stop in Harare on the way to Cape Town and quickly obtain an entry visa there.
With considerable help from Eva Poinar, I completed the paperwork for exporting the field-equipment to Cape Town, packed the equipment securely, found an international shipper reputed to be reliable, and shipped the Lewis-Lab field gear to Jenny Jarvis. Later I learned that Jenny was required to post a sizable bond in order bring all the suspicious-looking gear through South-African customs.
Namibia and the Golden Mole
In 1987, when he learned I was going to Cape Town, my colleague Tom Hetherington told me I ought to consider working on the golden mole—a tiny animal with massive ossicles, suggesting a middle ear adapted for inertial motion-sensing. In the early 1990s, Professor Tumarkin, a long-retired hearing researcher in Wales had sent me X-ray images of golden-mole skulls, showing the ossicles in place. They were impressive. By 1993 I was eager and ready to take on the golden mole. The Lewis-Lab field gear had been upgraded and was ready as well. It would be critical for our work.
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