Nebraskaland

54 NEBRASKAland • JULY 2015 Salt Creek Tiger Beetle Production booming in the lab. By Eric Fowler M ajor advancements in captive breeding have scientists cautiously optimistic about the future of the Salt Creek tiger beetle, the nation's most endangered insect, and this year will allow them to take further steps to expand the wild population of the insect, which last year numbered just 143. The captive breeding program begins in July with the capture of 15 pairs of adult beetles from their rare saline wetland habitat north of Lincoln. Those adults are allowed to breed and lay eggs in petri dishes filled with saline soil under the watchful eye of keepers at the Henry Doorly Zoo in Omaha. When the eggs hatch, the larvae are transferred to rearing containers and fed fruit flies and crickets through the summer. The insects are kept in incubators that mimic the climate and daylight conditions of the wild, and as is the case in the wild, they become less active, or even inactive, in the winter. In the spring, as temperatures warm, the larvae become active again and feeding resumes. In late May or early June, they are released into the wetlands. While wild tiger beetles spend two years as larvae, captive-reared insects emerge as adults in just one, a convenient result of the constant food supply they are given by zookeepers that speeds their growth. During the first two years of the program, which began in 2011, just 29 larvae were produced and only 11 survived to be released. Last spring, 832 larvae were produced, an exponential increase from an already impressive 332 reared in 2013, and about 60 percent of those survived through the winter. Mike Fritz, a biologist with the Nebraska Game and Parks Commission, which is partnering in the program with the U.S. Fish and Wildlife Service, the University of Nebraska- Lincoln, the Henry Doorly Zoo and the Lincoln Children's Zoo, with additional help from the City of Lincoln, Lower Platte South Natural Resources District and the Saline Wetland Conservation Partnership, said with so many larvae produced in 2013, they opted to keep 25 at the zoo and allow them to emerge as adults to boost the breeding stock. "Those adults laid far more eggs than the wild ones," Fritz said, noting that about two-thirds of this year's larvae came from the seven captive females that emerged. With another windfall in the breeding program this year, the scientists are again hedging their bets. In May, they released 416 larvae at four sites in the saline wetland complex to supplement wild populations. They also kept back 25 larvae that will be allowed to emerge as adults and breed, and the 100 or so adults they expect to emerge from another 190 rearing containers that have been left untouched will be released to hopefully breed in the wild. That decision could prove fortuitous, as heavy rains and flooding on Little Salt Creek a week after larvae were released inundated many sites where wild tiger beetles live and caused bank erosion that buried others, conditions that affected release sites as well. Similar flooding is suspected to have trimmed the wild population from 365 in 2013 to 143 in 2014. "We know we still have some alive, but that probably resulted in mortality in some of those larvae," Fritz said. "It may be very critical that we have those [captive-reared] adults out there to supplement the low wild population." Fritz said they may rely solely on captive-reared adults for breeding this year if the annual survey again shows a low count of wild adult beetles. The Salt Creek tiger beetle was listed as endangered in 2005. In 2014, the U.S. Fish and Wildlife revised the amount of habitat deemed critical for the species' recovery, including 1,110 acres along Little Salt, Rock, Haines Branch and Oak creeks. All of the habitat is in Lancaster and Saunders counties. Only 35 acres of habitat hold beetles, a fraction of the 20,000 acres of saline wetlands that historically were found in the region but lost to urban and agricultural development and stream channelization. A revision of the species' recovery plan is underway and expected to be complete this year. With that in hand, the next true test of the breeding program will come when larvae or adults are released in areas that previously held tiger beetles, allowing researchers to monitor survival that is difficult due to the presence of wild beetles in release sites. ■ PHOTO BY ERIC FOWLER Using a piece of sewing thread, Sarah Jenkins, keeper of butterflies and insects at the Henry Doorly Zoo in Omaha, "fishes" a Salt Creek tiger beetle larvae from its burrow in a petri dish where the egg from which it hatched was laid. This new technique, which takes advantage of the insect's predatory nature, has led to much greater survival of larvae than the previous method of simply breaking apart the soil to retrieve the larvae and transferring them to rearing containers.

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