{"title":"Late-season Reproduction in Western Toads (Bufo boreas)","authors":"Gregory B. Pauly, K. Delaney","doi":"10.3160/soca-116-02-147-151.1","DOIUrl":null,"url":null,"abstract":"Western toads (Bufo boreas, or Anaxyrus boreas of some authors) typically breed from late January to July depending on elevation, latitude, and local conditions (Sornborger 1979; Stebbins 2003; Thompson 2004; Muths and Nanjappa 2005). Generally, breeding takes place early in the active season and is explosive with the breeding season lasting only a few weeks with most of the breeding activity occurring in a few nights (Sornborger 1979; Olson et al. 1986; Muths and Nanjappa 2005; Pauly pers. obs.). At low elevation sites in Southern California, for example, breeding may begin as early as late January assuming rainfall has been adequate to fill breeding sites and stimulate activity. At higher elevation sites, breeding activity is triggered by warming conditions and snowmelt with toads breeding shortly after emerging from hibernation sites (Sornborger 1979; Olson et al. 1986; Fetkavich and Livo 1998; Hammerson 1999; Thompson 2004; Muths and Nanjappa 2005). Here we report unusually late breeding activity in western toads. On 9 November 2015, one of us (KSD) observed late stage tadpoles (up to Gosner Stage 43) at a seasonal pond in the Los Robles Open Space, Santa Monica Mountains, Ventura County, California (34.163226, −118.881964, elevation 370 m; Figs. 1, 2). The pond is oval with maximum size of 7 m by 5 m. No metamorphs were observed in the surrounding terrestrial habitat, but the presence of many tadpoles undergoing metamorphosis suggests that this late breeding event would result in metamorphs leaving the pond within a few days. Photographs of these tadpoles were submitted to the Reptiles and Amphibians of Southern California (RASCals) Citizen Science Project (iNaturalist 2365499) with additional photographs deposited in the Natural History Museum of Los Angeles County Photographic Collection (LACM PC 1998–2005). Breeding was likely triggered by an unusually large rain event on the morning of 15 September 2015 that filled this previously dry, temporary pond. This rain event resulted in part from lowlevel moisture from the former Eastern Pacific Hurricane Linda. Weather data from Los Angeles indicate the storm produced the second wettest September day on record (6.07 cm). Data from the nearest weather station in the Santa Monica Mountains, which is at Deals Flat, ca. 11.5 km southwest of the breeding site, are available via climateanalyzer.org. At Deals Flat, 3.3 cm of rain fell in this unusual storm event, which is more rain than fell in the previous February (2.18 cm) or March (1.78 cm) when B. boreas typically breeds in this area. The rain event also took place in the fourth year of a severe drought in Southern California, during which time B. boreas breeding activity was greatly reduced. To the best of our knowledge, the occurrence of tadpoles in November and an inferred breeding date in mid-September are the latest observations of breeding activity reported for B. boreas. Lemm (2006) noted that western toads breed from January to September, a slightly longer period than the January to July period suggested by Stebbins (2003), but no dates or locations of","PeriodicalId":90803,"journal":{"name":"Bulletin (Southern California Academy of Sciences)","volume":"36 1","pages":"147 - 151"},"PeriodicalIF":0.0000,"publicationDate":"2017-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Bulletin (Southern California Academy of Sciences)","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.3160/soca-116-02-147-151.1","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 1
Abstract
Western toads (Bufo boreas, or Anaxyrus boreas of some authors) typically breed from late January to July depending on elevation, latitude, and local conditions (Sornborger 1979; Stebbins 2003; Thompson 2004; Muths and Nanjappa 2005). Generally, breeding takes place early in the active season and is explosive with the breeding season lasting only a few weeks with most of the breeding activity occurring in a few nights (Sornborger 1979; Olson et al. 1986; Muths and Nanjappa 2005; Pauly pers. obs.). At low elevation sites in Southern California, for example, breeding may begin as early as late January assuming rainfall has been adequate to fill breeding sites and stimulate activity. At higher elevation sites, breeding activity is triggered by warming conditions and snowmelt with toads breeding shortly after emerging from hibernation sites (Sornborger 1979; Olson et al. 1986; Fetkavich and Livo 1998; Hammerson 1999; Thompson 2004; Muths and Nanjappa 2005). Here we report unusually late breeding activity in western toads. On 9 November 2015, one of us (KSD) observed late stage tadpoles (up to Gosner Stage 43) at a seasonal pond in the Los Robles Open Space, Santa Monica Mountains, Ventura County, California (34.163226, −118.881964, elevation 370 m; Figs. 1, 2). The pond is oval with maximum size of 7 m by 5 m. No metamorphs were observed in the surrounding terrestrial habitat, but the presence of many tadpoles undergoing metamorphosis suggests that this late breeding event would result in metamorphs leaving the pond within a few days. Photographs of these tadpoles were submitted to the Reptiles and Amphibians of Southern California (RASCals) Citizen Science Project (iNaturalist 2365499) with additional photographs deposited in the Natural History Museum of Los Angeles County Photographic Collection (LACM PC 1998–2005). Breeding was likely triggered by an unusually large rain event on the morning of 15 September 2015 that filled this previously dry, temporary pond. This rain event resulted in part from lowlevel moisture from the former Eastern Pacific Hurricane Linda. Weather data from Los Angeles indicate the storm produced the second wettest September day on record (6.07 cm). Data from the nearest weather station in the Santa Monica Mountains, which is at Deals Flat, ca. 11.5 km southwest of the breeding site, are available via climateanalyzer.org. At Deals Flat, 3.3 cm of rain fell in this unusual storm event, which is more rain than fell in the previous February (2.18 cm) or March (1.78 cm) when B. boreas typically breeds in this area. The rain event also took place in the fourth year of a severe drought in Southern California, during which time B. boreas breeding activity was greatly reduced. To the best of our knowledge, the occurrence of tadpoles in November and an inferred breeding date in mid-September are the latest observations of breeding activity reported for B. boreas. Lemm (2006) noted that western toads breed from January to September, a slightly longer period than the January to July period suggested by Stebbins (2003), but no dates or locations of
西部蟾蜍(Bufo boreas,或一些作者的Anaxyrus boreas)通常在1月下旬至7月繁殖,具体取决于海拔、纬度和当地条件(sornborg 1979;史泰宾斯2003;汤普森2004;Muths and Nanjappa 2005)。一般来说,繁殖发生在活动季节的早期,繁殖季节仅持续几周,大部分繁殖活动发生在几个晚上(sornborg 1979;Olson et al. 1986;Muths and Nanjappa 2005;保利珀耳斯。奥林匹克广播服务公司)。例如,在南加州的低海拔地区,如果降雨量足以填满繁殖地并刺激活动,繁殖可能早在1月底就开始了。在海拔较高的地方,繁殖活动是由变暖和融雪引发的,蟾蜍在从冬眠地点出来后不久就会繁殖(sornborg 1979;Olson et al. 1986;Fetkavich and Livo 1998;之一Hammerson 1999;汤普森2004;Muths and Nanjappa 2005)。在这里,我们报告了西方蟾蜍不寻常的晚期繁殖活动。2015年11月9日,我们中的一位(KSD)在加利福尼亚州文图拉县圣莫尼卡山脉Los Robles开放空间的一个季节性池塘中观察了晚期蝌蚪(直至Gosner阶段43)(34.163226,- 118.881964,海拔370米;图1、图2).池塘呈椭圆形,最大尺寸为7米× 5米。在周围的陆地栖息地没有观察到蜕变,但许多蝌蚪正在经历蜕变,这表明这种晚期繁殖事件将导致蜕变在几天内离开池塘。这些蝌蚪的照片提交给南加州爬行动物和两栖动物(rascal)公民科学项目(iNaturalist 2365499),其他照片存放在洛杉矶县自然历史博物馆摄影集(LACM PC 1998-2005)。繁殖可能是由于2015年9月15日上午的一场异常大雨事件引发的,雨水填满了这个以前干燥的临时池塘。这次降雨事件的部分原因是来自前东太平洋飓风琳达的低空水分。来自洛杉矶的天气数据显示,这场风暴造成了有记录以来9月份第二潮湿的一天(6.07厘米)。来自圣莫尼卡山脉最近的气象站的数据可通过climateanalyzer.org获得,该气象站位于繁殖地点西南约11.5公里处的Deals Flat。在迪尔斯平原,这场不寻常的风暴带来了3.3厘米的降雨,比之前2月(2.18厘米)或3月(1.78厘米)的降雨量还要多,而这两个季节正是北方白蝽在该地区典型繁殖的季节。这次降雨事件也发生在南加州严重干旱的第四年,在此期间北蝽的繁殖活动大大减少。据我们所知,蝌蚪在11月出现,推断繁殖日期在9月中旬,这是对北方圆蝽繁殖活动的最新观察报告。Lemm(2006)指出,西部蟾蜍的繁殖周期为1月至9月,比Stebbins(2003)提出的1月至7月略长,但没有日期和地点