Conservation Northwest

Predator and prey Extraordinary variation Pallid bat with centipede. © Merlin D. Tuttle, Bat Conservation International, www.batcon.org Predator of the night sky In the growing twilight of a summer evening, shadows flit and dart just above the surface of a lake and around your head. Witness the nightly hunt of the world's only flying mammal and one of the sky's most ubiquitous predators: the bat. No matter where you are in the Northwest, you aren't very far from one of at least fifteen species of bat, which consume a huge amount of insects and other invertebrates every night. Most Northwest bats hunt on the wing using echolocation: emitting high pitched sound waves that bounce off prey to create a sort of sound "map." Bats often scoop insects into their wing or tail membranes as they fly, causing their characteristic, erratic flight. The pallid bat of eastern Washington (Antrozous pallidus) flies low to the ground, listening for beetles, scorpions, and other invertebrates to scuffle by before the pallid bat drops in for a crawling hunt. The hoary bat (Lasiurus cinereus), one of the largest Northwest bat species can catch small rodents and even other bats. While a lot of people misunderstand bats, most of us are pretty happy to have their predatory instincts control night-flying insects like mosquitoes! A single little brown bat (Myotis lucifigus), with a body no bigger than an adult's thumb, can eat up to 8 grams—2 grapes worth—of insects a night, which adds up to a lot when you consider the sheer number of bats on the wing with life spans of up to 30 years! Farmers have long appreciated bats' role in protecting crops by controlling insects. Studies estimate bats annually provide from $3.7 billion to $53 billion in pest control services to US agriculture. That's one important predator! We can help bats and their insect-eating service by protecting their habitat, reducing pesticide use, and aggressively researching White Nose Syndrome, which has already killed more than 1 million bats in the eastern US. Wind power turbines must also be sited and operated with bat migratory routes and flight habits in mind. To help create habitat, build your own backyard bat box. Email barbara@conservationnw.org for simple plans. The night sky is full of dipping and darting bug-eating predators; keep an eye out as the sun goes down! —Barbara Christensen Keeping the Northwest wild Keeping the Northwest wild Perhaps the most important predators in the world, at least from the standpoint of sheer numbers, are spiders. They exhibit extraordinary variation. To date, there are at least 40,000 described species worldwide. There are even spiders that swim. Spiders are voracious predators. They eat enormous numbers of insects, and they will eat anything, from leafhoppers to honey bees to predatory beetles. Spiders divide into two distinct groups. The mygalomorphs, called "primitive" spiders, have fangs that point downwards. Tarantulas are our most famous example. Mygalomorphs are distinguished from the araneomorphs, or "modern" spiders, whose fangs strike together horizontally. Most spiders you will see, from the beautiful orb weavers on your rose bushes to wandering, giant house spiders trapped in the bathtub, are araneomorphs. The small spider on your windowsill, which cannily stops and turns to look at you, is likely a jumping spider. Their family name is Salticidae, as in the Spanish, saltir: to leap. Salticiae is the largest of all spider families with 5,200 described species, 300 in the US alone. Sophisticated hunters, salticids are also considered the smartest in this insect group. They hunt by sight— stalking, chasing Bold jumping spider with ant. © Kitty Todd down, and leaping onto flies or other prey. Recent research has used jumping spiders in the genus Portia to study cognitive attributes that are more similar to large predatory mammals, such as lions, than to very small spiders. "What makes salticids special is their unique, complex eyes and acute eyesight," write Robert Jackson and Duane Harland of the University of Canterbury, New Zealand. "Large anterior medial eyes give them an almost catlike appearance. No other spider has eyes like these and no other spider has such intricate vision-guided behaviour.... a better common name for salticids would probably by 'eightlegged cats.'" Even extreme arachnophobes do not seem to be frightened of jumping spiders. Australian entomologist Barry Richardson explains, "They move differently. They act differently. They're not spiders," he concludes, "they're salticids." —Erin Moore Spring/Summer 2011 Spring/Summer 2011 9 9

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