Meeting Abstract
1.5 Sunday, Jan. 4 Deciding when to hatch: Predator and embryo cues in wasp-induced hatching of red-eyed treefrogs HUGHEY, M.C.*; ROGGE, J.R.; WARKENTIN, K.M.; Boston University, Boston; Boston University, Boston; Boston University, Boston mchughey@bu.edu
Predator-induced hatching allows embryos to avoid predation, but to be effective embryos must accurately assess and respond to threats. Red-eyed treefrog (Agalychnis callidryas) embryos face many natural enemies, including wasps (Polybia rejecta). Embryos can hatch up to 30% early in response to wasp attack, even without direct contact with wasps. Embryos are unresponsive to wasp vibrations alone; they may use other cues from wasps or cues from neighboring embryos to inform hatching. We assessed cues used by embryos when deciding to hatch during wasp attacks. We videotaped wasp attacks that induced hatching at a feeding station where wasps were trained to forage. From the videos, we identified the first and last five embryos to hatch from a clutch and characterized their experiences during the time period when the first five embryos were hatching (N = 103 focal embryos). We quantified behavior of focal embryos, neighboring and more distant embryos, and wasps. We compared experiences of focal embryos that hatched 1) during the sampled period vs. later, 2) with vs. without direct wasp attack, and 3) early, but without direct attack, vs. later. We also assessed which wasp and embryo behaviors best predicted hatching. Embryos that hatched experienced substantial wasp activity on or near them, while for later-hatching embryos wasp activity was mostly farther away. Both focal hatching embryos and their close neighbors were more active than later-hatching embryos and neighbors. Embryos that hatched without direct wasp contact nonetheless experienced high amounts of wasp activity nearby. Red-eyed treefrog embryos thus assess risk on a fine spatial scale in wasp attacks and appear to use cues from both wasps and other embryos when deciding to hatch.
