Use of Implanted Radiotransmitters to Estimate Survival of Greater Sage-Grouse Chicks

ABSTRACT Reduced chick survival has been implicated in declines of greater sage-grouse (Centrocercus urophasianus) populations. Because monitoring survival of unmarked sage-grouse chicks is difficult, radiotelemetry may be an effective technique to estimate survival rates, identify causes of mortality, and collect ecological data. Previous studies have used subcutaneous implants to attach radiotransmitters to hatchlings of several species of birds with precocial young. Previous researchers who used subcutaneous implants in free-ranging populations removed chicks from the capture location and implanted transmitters at an alternate site. Because logistics precluded removing newly hatched greater sage-grouse chicks from the field, we evaluated a method for implanting transmitters at capture locations. We captured 288 chicks from 52 broods and monitored 286 radiomarked chicks daily for 28 days following capture during May and June 2001–2002. Two (>1%) chicks died during surgery and we did not radiomark them. At the end of the monitoring period, 26 chicks were alive and 212 were dead. Most (98%, 207/212) radiomarked chick mortality occurred < 21 days posthatch and predation (82%, 174/212) was the primary cause of death. Necropsies of 22 radiomarked chicks did not indicate inflammation or infection from implants, and they were not implicated in the death of any chicks. Fate of 48 chicks was unknown because of transmitter loss (n = 16), radio failure (n = 29), and brood mixing (n = 3). Overall, the 28-day chick survival rate was 0.220 (SE = 0.028). We found that mortalities related to the implant procedure and transmitter loss were similar to rates reported by previous researchers who removed chicks from capture sites and implanted transmitters at an alternate location. Subcutaneous implants may be a useful method for attaching transmitters to newly hatched sage-grouse chicks to estimate survival rates, identify causes of mortality, and collect ecological data.     

Alarm response of hatchlings of the apple snail, <Emphasis Type="Italic">Pomacea canaliculata</Emphasis> (Gastropoda: Ampullariidae), to aqueous extracts of other individuals

We examined how hatchlings of the freshwater snail, Pomacea canaliculata, responded to aqueous extracts of conspecific hatchlings. Three, 3-day-old hatchlings were macerated in deionized water (1mg hatchling per 1ml water). When 0.5ml of the aqueous extract was added to a test tube containing 10 hatchlings of the same age and 50ml of water, the hatchlings in the water began to crawl out of the water within 5min. The proportion of hatchlings that crawled out of the water approached 0.6–0.9 after 1h, but gradually decreased to 0.4 after 24h. The relatedness between the live and the macerated hatchlings had no significant influence on the response. Hatchlings of egg masses obtained either in the laboratory or in the wild responded similarly to aqueous extracts of hatchlings from either egg mass. This suggests that the conditions under which the egg masses were incubated or the conditions that their parents had experienced had no effect on the hatchlings response. When compared with experiments reported on other aquatic animals, we consider the behavior of the hatchlings to be an alarm response of escaping from predators.     

Hatchling Size and Aspects of Biology in the Deep-Sea Amphipod Genus Eurythenes (Crustacea: Amphipoda)

Records attributed to Eurythenes gryllus are discussed in the light of described morphological variation, and the existence of a third species in the genus is postulated. The presence of five pairs of oostegites in E. gryllus, a character almost unique among the Amphipoda, is confirmed. Brooding females of E. gryllus and E. obesus, captured in deep midwater hauls in the eastern North Atlantic Ocean, are reported for the first time. The 120 mm E. gryllus female carried 237 hatchlings (mean length 11.13 mm) and the 48 mm E. obesus female 47 hatchlings (mean length 7.99 mm). Hatchlings showed variability in size and bodily proportion, and measurements of individual body segments could not be used to predict overall length. Despite this variability, no evidence for more than one instar was found. The hatchlings of E. gryllus are established as a hitherto unrecognized instar in this species. Egg size for E. gryllus and E. obesus is predicted. The biological consequences of the absolute and relative size of hatchling in the two species, and the depths of capture of the E. gryllus female, are discussed.     

Dispersal by gray ratsnakes: Effects of sex,age and time

Dispersal is one of the most fundamental components of ecology. Dispersal is also particularly relevant in an era of unprecedented habitat loss and climate change. We used a unique dataset to examine dispersal in gray ratsnakes (Pantherophis spiloides). Over a decade, we marked and released >1,500 hatchlings while monitoring the population of ratsnakes over a large area (≈1,900 ha). We tested the hypotheses that dispersal should be (a) largely restricted to within the local population given previous genetic evidence of limited gene flow at greater distances and (b) male biased because male gray ratsnakes are under strong sexual selection. We recaptured 69 gray ratsnakes that had been marked as hatchlings after periods ranging from 1 day to 11 years. We found that dispersal distance increased with time, but was not significantly sex-biased, and that gray ratsnakes are extremely faithful to their communal hibernacula (only 2.8% of 497 juvenile and adult ratsnakes captured at least twice at communal hibernacula changed sites between years). Thus, dispersal is largely limited to the period from hatching until an individual joins a communal hibernaculum. Based on the spatial patterns of dispersal we observed, the most plausible explanation for dispersal is that hatchling ratsnakes disperse from their natal site to join a neighboring communal hibernaculum. Our study yielded the most reliable data on dispersal distances from birth by a snake to date.     

Plasticity and limitations of extended egg retention in oviparous Zootoca vivipara (Reptilia: Lacertidae)

The transition between oviparity and viviparity in reptiles is generally accepted to be a gradual process, the result of selection for increasingly prolonged egg retention within the oviduct. We examined egg retention plasticity in an oviparous strain of the lacertid lizard Zootoca vivipara, a species having both oviparous and viviparous populations. We forced a group of female Z. vivipara to retain their clutch in utero by keeping them in dry substrata, and assessed the effect on embryonic development and hatching success, along with offspring phenotype and locomotor performance. Forced egg retention for one additional week affected the developmental stage of embryos at oviposition, as well as hatchling robustness and locomotor performance. However, embryos from forced clutch retention treatment reached one stage unit more than control embryos at oviposition time. Embryos from control eggs were more developed than embryos from experimental eggs after approximately the same period of external incubation, showing that embryonic development is retarded during the period of extended egg retention, despite the high temperature inside the mother's body. Significant differences in external incubation time were only found in one of the two years of study. Hatching success was much lower in the experimental group with forced egg retention (21.1%) than in the control group (95.4%). Therefore, we conclude that there are limitations that hinder the advance of intrauterine embryonic development beyond the normal time of oviposition, and that extended egg retention does not represent clear advantages in this population of Z. vivipara. Nevertheless, the fact that some eggs are successful after forced egg retention could be advantageous for the females that are able to retain their clutch under unfavourable climatic conditions. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 75–82.     

Latitudinal differences in temperature effects on the embryonic development and hatchling phenotypes of the Asian yellow pond turtle,Mauremys mutica

The effect of incubation temperature on embryonic development and offspring traits has been widely reported for many species. However, knowledge remains limited about how such effects vary across populations. Here, we investigated whether incubation temperature (26, 28, and 30 °C) differentially affects the embryonic development of Asian yellow pond turtle (Mauremys mutica) eggs originating from low‐latitude (Guangzhou, 23°06′N) and high‐latitude (Haining, 30°19′N) populations in China. At 26 °C, the duration of incubation was shorter in the high‐latitude population than in the low‐latitude population. However, this pattern was reversed at 30 °C. As the incubation temperature increased, hatching success increased in the low‐latitude population but slightly decreased in the high‐latitude population. Hatchlings incubated at 30 °C were larger and righted themselves more rapidly than those incubated at 26 °C in the low‐latitude population. In contrast, hatchling traits were not influenced by incubation temperature in the high‐latitude population. Overall, 30 °C was a suitable developmental temperature for embryos from the low‐latitude population, whereas 26 and 28 °C were suitable for those from the high‐latitude population. This interpopulation difference in suitable developmental temperatures is consistent with the difference in the thermal environment of the two localities. Therefore, similarly to posthatching individuals, reptile embryos from different populations might have evolved diverse physiological strategies to benefit from the thermal environment in which they develop. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 114 , 35–43.     

温度、湿度对黄喉拟水龟胚胎发育的影响

在9种不同温湿度组合条件（25 ℃和-12 kPa、29 ℃和-12 kPa、33 ℃和-12 kPa、25 ℃和-150 kPa、29 ℃和-150 kPa、33 ℃和-150 kPa、25 ℃和-300 kPa、29 ℃和-300 kPa、33 ℃和-300 kPa）下孵化了黄喉拟水龟卵,研究了温度对黄喉拟水龟卵孵出幼体特征的影响及其与湿度的相互作用对孵化期、孵化成功率和孵出幼体特征的影响.结果表明：黄喉拟水龟卵的初始质量、孵化温度、湿度及温湿度相互作用均显著影响孵化过程中卵质量的增加;同一温度下,孵化湿度越高,卵的终末质量越大;而孵化卵的终末质量与孵化温度并不呈线性相关;孵化温度显著影响黄喉拟水龟卵的孵化期,温度越高、孵化期越短,孵化湿度及温湿度相互作用对孵化期的影响不显著;孵化温度和湿度显著影响孵化成功率和卵壳龟裂率;25 ℃和33 ℃处理组孵出幼体中发现畸形个体,而29 ℃处理组中未发现;孵化温度显著影响孵出幼体的质量、背甲长和宽、腹甲长和宽、体高和尾长;孵化湿度只对孵出幼体的背甲长有影响,对其他被检测的幼体特征无显著影响;温湿度的相互作用对所有被检测的孵出幼体特征无叠加或减弱的显著影响.     

孵化温度对白条草蜥孵出幼体大小、形态和运动表现的影响

实验用白条草蜥(Takydrous wolteri）卵由1999年和2000年4月捕自安徽滁州的19条成年雌体产出。用4个恒定温度（24-33℃）孵化白条草蜥卵,检测孵化温度对孵出幼体大小、形态和运动表现的影响。孵化卵从环境中吸不导致生量增加,卵重量增加与卵初始重量和孵化温度有关。24、27、30和33℃孵化期的平均值分别为41.9、30.6、6.25和22.6d。温度显著影响孵化成功率及孵出幼体的湿重、躯干干重和剩余卵黄干重,但对孵出幼体的性别、体长、尾长和干重无显著影响。24℃和27℃孵出幼体湿重和躯干干重大于33℃孵出幼体,剩余卵黄干则小于33℃孵出幼体;30℃和33℃孵出幼体的湿重、躯干干重和剩余卵黄干重无显著差异。孵化温度显著影响孵出幼体一些局部形态特征：24℃和27℃孵出幼体头长和头宽矫正值显著大于高温（33℃）孵出幼体,24℃孵出幼体耳径正值一般小于较高温度孵出的幼体。疾跑速与幼体体长成正相关,与幼体尾长和状态无关。高温孵出幼体运动能力较差。雄笥幼体腹鳞行数少于雌性幼体,尾长和后肢长大于雌性幼体,这些特征的两性差异与孵化温度无关。孵化热环境能诱导白条草蜥部分表型特征的变异,这些特征的变异可能对个体的适应性具有长期的影响。     

多疣壁虎的雌性繁殖及孵化温度对孵化期和孵化幼体特征的影响

多疣壁虎 (Ｇｅｋｋｏｊａｐｏｎｉｃｕｓ)是华东地区蜥蜴区系的重要成分 ,向西分布至四川东部 ,向北分布至甘肃和陕西南部 ,国外见于朝鲜南部和日本部分岛屿[7,3 2 ] 。有关该种的生态学研究已涉及 ,①雌雄两性异形和繁殖习性[4 ,16,2 4 ] ;②卵孵化和温度决定性别[3 ,17,2 6,2 7] ;③贮能部位及各部位的年变化和相对重要性评估[1,16] ;④温度对摄食量和食物同化的影响[2 ] ;⑤胚胎和成体的代谢率[6,13 ,3 0 ,3 1] 。浙江杭州产多疣壁虎年产 1～ 3窝卵 ,窝卵数通常恒定为 2枚 ,大个体产多窝卵 ,第 1窝卵和第 2窝卵的卵重无显著差异[4 ] 。…