The mating system of the Weddell seal, Leptonychotes weddelli

Metadata record for data from ASAC Project 2184
See the link below for public details on this project.

The objectives of this project were:

To characterise the mating system of the Weddell seal by:
1) acoustically tracking males under the ice during the breeding season,
2) measuring changes in health and condition of individual males over the breeding season,
3) determining whether vocalisations are used as advertisements of individual quality to attract females, and/or in male-male competition,
4) develop and use a combination of microsatellite loci tests to assign paternity to newborn pups, and then use these results to determine whether the variance in male mating success is related to territory size, tenure and/or individual characteristics.

A large number of collected data files are available for download. Many files are in an unknown format, but will open with a standard text editor. See below for summaries of the two seasons of fieldwork.

1997/1998 Season:
In November/December 1997, we conducted a pilot study at the Turtle Rock colony (77.727S, 166.85E) in McMurdo Sound. All of the techniques outlined in the proposal were successfully trialled. Acoustic pingers were attached to seven males and five females for a total deployment of 104 seal days and mass and morphometrics obtained for each animal. Preliminary analysis of male movements indicate that males held adjacent yet non-overlapping territories on the southern side of Turtle Rock, along a major ice crack and where the congregation of females was highest. Both the size and shape of the males territories, and the evidence from the vocalisation data show that we captured the dominant males at the site.
Both males and females were immobilised using Ketamine/Diazepam with no loss of an animal, nor signs of respiratory depression. Vocalisations were recorded from all territory holding males, and both behavioural and vocal responses of both male and female seals to familiar and unfamiliar calls were observed. We bleach marked all animals to which we attached pingers and these markings were visible on our under-ice video - with which we also recorded behavioural responses to both animals and our under-ice speaker during playback experiments. We conducted a daily census of all animals at Turtle Rock and above-ice movements were recorded. Skin samples were taken from 24/25 males seen at the site and 43/45 mother-pup pairs (One male was only seen on a single occasion at the colony, though sighted elsewhere, and two females disappeared shortly after our arrival at the colony).

Significant findings
Dominant males hold under-ice territories which are adjacent yet non-overlapping - however territory boundaries change considerably over the course of the breeding season. Males respond to playbacks of their own and others calls as do females. Females towards the end of lactation will visit each males territories. Whether to assess individual males or not is yet to be determined.

1998/1999 Season
Between October 29 through December 10 1998, the behaviour of male and female weddell seals at the Turtle Rock colony (77.727S, 166.85E) were monitored both above and below the ice. This season, we switched from the seal sled method of capture and restraint (see K027 report 1997) to the use of a pole net and tripod. Seals were bagged by placing a seal hood over their head and then a 3m pole net (consisting of two, 3m long poles connected by a 2m wide, 2.5cm mesh, net , was placed over them and the poles tied tightly at both ends, leaving them constrained within the netting bag. The pole net was then hoisted under a tripod (built by Antarctica New Zealand) using a chain block suspended from the head of the tripod, and the animal weighed using electronic scales. For attachment of instruments, animals were immobilised with an intra-muscular injection of Ketamine/Diazepam at a dose rate of approximately 2.0mg/100 kg Ketamine, 0.4mg/100 kg Diazepam as was used successfully in 1997. Animals were only immobilised for attachment of instruments with HR electrodes (ie 3 males and 7 females). Animals were not immobilised for removal of instruments with the exception of one female who was particularly active. A small number of untagged animals were tagged in the rear flippers using tags provided by the University of Minnesota Weddell seal program as part of their long-term studies of the McMurdo Sound Weddell seal population. Maximum animal handling time including gluing of instruments and allowing for equilibration of isotopes (see below) was approximately 3 hours/seal. The mass of animals at first and last capture is shown in Table 1 below.

Animal Movements - Males: Movements under the ice were monitored using depth modulated acoustic transmitter (Vemco V16P). An array of three hydrophones, each approximately 500m apart, was placed around the colony on the southern side of Turtle Rock.. The position of each animal (x, y, z locations) was automatically logged when it was underwater at intervals of between 15 and 60 sec. The array was powered continuously using 12V dry-fit batteries connected in series. A VHF radio transmitter (Sirtrack) was glued to the dorsal surface of each male using a quick-dry Epoxy (Araldite). Time depth recorders (MkV1) Heart rate loggers, and an Acoustic Heart Transmitter were attached to three males. The VHF transmitter was used to assist in relocating animals that left the study site during the breeding season and to monitor time spent on the ice via a Televilt Scanning receiver mounted atop a Wannagan placed near the SW side of Turtle Rock. The position of males on the surface at the colony was also mapped approximately once every two days.

Females: Under ice movements and feeding behaviour of six females was monitored by attachment of acoustic pingers as outlined above. We attached Time depth recorders (MkV1) Heart rate loggers, and an Acoustic Heart Transmitter to each of five of these females, the sixth did not appear to transmit heart-rate. A seventh female was captured but no instruments fitted, as she did not respond to the immobilising agents.

Energetics -Body composition of 12 males was determined by measuring total body water using hydrogen isotope dilution on two separate occasions. At first capture, a blood sample (5ml) was drawn directly into Vacutainer collection tubes from the femoral vein at the base of the rear flippers using a 1 * inch, 18g needle and each animal was then injected with 5ml tritiated water (HTO) (specific activity 1 mCi per ml). The animal was then weighed as outlined above. Unless further instrument attachment was to occur, the animal was then released in order to allow the HTO to equilibrate with the body water pool (approximately three hours), and later recaptured for a second blood sample to be taken. Recapture and sampling usually took less than 10min. The blood samples were allowed to settle in the warmth of the Apple in the field and the serum fraction separated. Aliquots of serum were then held frozen for later analysis in Australia at the University of Tasmania. This procedure was repeated later in the season, and the changes in mass and TBW will be used to estimate energy expenditure (Reilly and Fedak 1991).

Mass changes are shown in Table 1.
Seal Tag Name Mass1 (kg) Mass2 (kg) Mass loss Seal Days Rate of mass lost/day
Purple 37 #1 Dudley 413.5 354.5 59 24 2.46
Purple 547 #2 Shed 369.5 319.5 50 20 2.50
Pink 928 #3 385.5 338.5 47 22 2.14
Red CT 283/965 #4 352.5 304.5 48 22 2.18
White 423 #5 King C 455 428.5 26.5 22 1.20
Pink 981 #6 Whiteboy 370.5 331.5 39 17 2.29
Y1339 #7 405.5 384.5 21 15 1.40
Pink CT 549 #8 Joe 362 325.5 36.5 15 2.43
Y1299 #9 Markboy 314.5 280.5 34 16 2.13
Orange CT 842 #10 344.5 293.5 51 14 3.64
Purple 808 #11 337.5 . .
Red 347 #12 313.5 . .

2) Function of Vocalisations

Method:
Hydrophones were used to obtain several recordings of five major call types from 8 of our captured males (pinger frequency allowed us to distinguish between individuals occupying the array). Following the 1999 field season, a correlational analysis will be used to determine if information on male characteristics (assessed using our physiological measures of their health or "quality") are revealed by vocalisations of the males we sampled over the three field seasons. Our current total sample size for this component of the research stands at 13 (1997 and 1998). It has become increasingly clear that the Long Trill calls, produced exclusively by males, may play important role in attracting females and challenging rivals. Two playback experiments were conducted to examine the function(s) of this important vocalisation, and other call types used by males. In the first experiment (initiated in 1997), the responses of 8 monitored males and a single female to the playback of each major call type and a control sound (walrus calls) were examined according to a systematic experimental schedule. For both males and females, we were able to record changes in position relative to the underwater speaker (using data from the pinger array), vocal behaviour (using a DAT recorder and a pair of hydrophones), activities near the playback speaker (using three underwater video cameras), swimming speed and heart rate of specific animals. Our current total sample size for this component of the research stands at 13 males and 2 females (1997 and 1998). The second experiment (also initiated in 1997) examined male-male competition and inter-sexual call function more directly. Our pilot study showed that males actively overlap the Long Trill songs of rivals with their own Trills, in a manner that is similar to territorial songbirds. We conducted "interactive" playback experiments to examine the consequences of overlapping the Long Trill calls of rivals. Five consecutive Long Trill calls of specific resident males (identified using a "real time" field spectrograph) were either (1) completely overlapped, (2) partially overlapped or (3) preceded by the recorded Long Trill calls of an unfamiliar male. A MiniDisc player was used to broadcast these calls to different resident males according to a systematic schedule. Underwater video cameras, the pinger array and hydrophones were then used to record the changes in patterns of under-ice movements and the vocal responses of 4 males and 5 females. Our current total sample size for this component of the research now stands at 7 males and 8 females (1997 and 1998). We also obtained continuous sound and video samples of male and female Weddell seals occurring along the main ice crack at Turtle Rock using a timelapse VCR connected to fixed video cameras and a hydrophone.

3) Paternity analysis: collection of samples

Method
The mating success of males at Turtle Rock will be determined by laboratory analysis of skin samples (6 mm diameter). These were collected from the edge of the interdigital webbing of the hind flipper using a leather punch, from all males, females and pups in 1997 and 1998, with further collections planned for 1999 and 2000. Samples were stored in eppendorf tubes filled with 100% ethanol. Sample degradation is minimal using this technique. Analysis has still to be conducted. This season we trialled a new technique for sampling using a small biopsy punch on the end of a pole but this technique proved unsatisfactory as biopsy heads became blunt after only 2-3 animals had been sampled. However, the clipping technique proved so successful that an experienced clipper could remove samples with such discretion that at times the animal being sampled did not wake.

Significant findings
Some of the results from the first year of this study were presented at the SCAR conference in Christchurch last August, and the abstract published in the NZ Natural Sciences series.
Harcourt, R.G., Hindell, M.A. and Waas, J.R. 1998. Under-ice movements and territory use in free-ranging Weddell seals during the breeding season. New Zealand Natural Sciences 23: 72-73
One of the most interesting findings relates to the interpretation of three dimensional dive profiles. One paper on three dimensional dive profiles in free-ranging Weddell seals is nearing completion. Other planned papers include measurement of heart-rate during diving, female foraging behaviour, communication and territorial behaviour, as well as the major reproduction papers.

本元数据记录关联ASAC项目2184（ASAC Project 2184）所产生的数据集，项目公开详情可参阅下方链接。

本项目的研究目标为：通过以下方式解析威德尔海豹（Weddell seal）的交配系统：
1) 声学追踪繁殖季冰下的雄性个体；
2) 监测繁殖季内单个雄性个体的健康与身体状况变化；
3) 确定威德尔海豹是否通过鸣叫声作为个体质量的展示信号，以吸引雌性，或用于雄性间的竞争；
4) 开发并结合微卫星位点检测（microsatellite loci tests）技术为新生幼崽确定父系身份，随后利用所得结果分析雄性交配成功率的差异是否与领地面积、任职时长及/或个体特征相关。

本次研究采集的大量数据文件均可下载。多数文件格式未标注，但可通过标准文本编辑器打开。下文将汇总两次野外考察季的工作概况。

1997/1998考察季：
1997年11/12月，研究团队在麦克默多湾的特特尔岩繁殖群（77.727°S，166.85°E）开展试点研究。方案中拟定的所有技术手段均顺利完成试点测试。研究团队为7只雄性与5只雌性个体部署了声学追踪信标，总有效部署时长为104海豹日，并为每只个体测量了体重与形态学指标。对雄性移动模式的初步分析显示，雄性个体在特特尔岩南侧沿一处大型冰裂缝区域划定相邻但不重叠的领地，该区域雌性聚集密度最高。雄性领地的面积与形态，结合鸣叫声数据的佐证均表明，本研究捕获了该区域的优势雄性个体。

所有雌雄个体均采用氯胺酮/地西泮（Ketamine/Diazepam）进行麻醉，无个体死亡或呼吸抑制症状出现。研究人员记录了所有领地雄性的鸣叫声，并观测到雌雄海豹对熟悉与陌生鸣叫声的行为与声学反应。研究团队为所有部署了信标的个体进行了漂白标记，这些标记可在冰下视频中清晰识别；借助冰下视频，研究人员同时记录了海豹在播放实验中对同类个体与水下扬声器的行为反应。研究人员每日对特特尔岩区域的所有个体进行种群普查，并记录海豹的冰上移动情况。研究人员采集了该区域观测到的24/25只雄性个体，以及43/45对母幼对的皮肤样本（其中1只雄性仅在繁殖群内被观测到1次，但在其他区域曾被发现；另有2只雌性在研究团队抵达后不久失踪）。

### 重要研究发现
优势雄性个体拥有相邻但不重叠的冰下领地，但领地边界在繁殖季内会发生显著变化。雄性与雌性均会对同类自身与其他个体的鸣叫声回放产生反应。处于哺乳期后期的雌性会造访每一处雄性领地，目前尚未明确雌性是否会借此评估雄性个体质量。

1998/1999考察季
1998年10月29日至12月10日期间，研究团队在特特尔岩繁殖群（77.727°S，166.85°E）开展野外工作，对冰上与冰下的威德尔海豹雌雄个体行为进行监测。本季研究改用杆式网具与三脚架替代此前的海豹雪橇抓捕固定法（详见1997年K027报告）。
抓捕时，先将海豹头罩套在海豹头部，随后将3米杆式网具（由两根3米长杆与2米宽、2.5厘米网眼的网面组成）罩住海豹，将杆两端捆绑收紧，使海豹被限制在网袋内。随后通过三脚架（由新西兰南极局建造）顶端悬挂的链式起重机将网具吊起，利用电子秤称量海豹体重。为部署仪器，研究团队采用1997年验证成功的麻醉方案：通过肌肉注射氯胺酮/地西泮，剂量为每100千克体重注射2.0mg氯胺酮与0.4mg地西泮。仅在部署心率电极时需要对个体进行麻醉（共3只雄性与7只雌性）；仅在1只异常活跃的雌性个体移除仪器时，才对其实施了麻醉。研究团队为少量未标记个体在后鳍肢佩戴明尼苏达大学威德尔海豹研究项目提供的标记物，该项目长期监测麦克默多湾的威德尔海豹种群。单只海豹的最长处理时长（包括仪器黏附与同位素平衡等待时间，详见下文）约为3小时。单只海豹首次与末次捕获时的体重详见下表1。

#### 个体移动
##### 雄性个体
冰下移动监测采用深度调制声学发射器（Vemco V16P）。研究团队在特特尔岩南侧繁殖群周边部署了由三台水听器（hydrophones）组成的监听阵列，各水听器间距约500米。当海豹处于水下时，系统会以15至60秒的间隔自动记录其三维位置坐标（x、y、z轴）。该阵列采用串联的12V干电池持续供电。研究人员使用快干环氧树脂（Araldite）将甚高频无线电发射器（VHF radio transmitter, Sirtrack）黏附在每只雄性个体的背侧。为3只雄性个体部署了时间深度记录仪（Time depth recorders, MkV1）、心率记录仪与声学心脏发射器。甚高频无线电发射器用于辅助定位繁殖季内离开研究区域的个体，并通过安装在特特尔岩西南侧Wannagan平台上的Televilt扫描接收机监测海豹的冰上停留时长。研究人员约每两天对繁殖群冰面的雄性个体位置进行一次测绘。

##### 雌性个体
研究团队通过上述声学信标技术监测了6只雌性的冰下移动与觅食行为。为其中5只雌性部署了时间深度记录仪（MkV1）、心率记录仪与声学心脏发射器，第6只个体未检测到心率信号传输。另有1只雌性个体被抓捕，但因对麻醉药物无反应，未部署任何仪器。

#### 能量代谢
通过两次氢同位素稀释法测定总身体水量，以此分析12只雄性个体的身体组成。首次捕获时，研究人员使用1英寸18G针头从后鳍肢基部的股静脉采集5ml血液样本至Vacutainer采血管中，随后为每只个体注射5ml氚化水（tritiated water, HTO，比活度为1mCi/ml）。随后按照前述方法称量海豹体重。若无需额外部署仪器，则将海豹释放，等待氚化水与体内水池达到平衡（约3小时）后，再次抓捕并采集第二份血液样本。二次抓捕与采样过程通常耗时不超过10分钟。血液样本在野外工作站的保温环境中静置分离血清，分装后的血清样本被冷冻保存，待后续送往澳大利亚塔斯马尼亚大学进行分析。本季后期重复了该实验流程，体重与总身体水量的变化将用于估算能量消耗（Reilly与Fedak，1991）。

体重变化情况详见表1：
| 海豹标记编号 | 首次体重(kg) | 末次体重(kg) | 体重损失量(kg) | 有效天数 | 日均体重损失量(kg/天) |
|--------------|--------------|--------------|----------------|----------|-----------------------|
| Purple 37 #1 Dudley | 413.5 | 354.5 | 59 | 24 | 2.46 |
| Purple 547 #2 Shed | 369.5 | 319.5 | 50 | 20 | 2.50 |
| Pink 928 #3 | 385.5 | 338.5 | 47 | 22 | 2.14 |
| Red CT 283/965 #4 | 352.5 | 304.5 | 48 | 22 | 2.18 |
| White 423 #5 King C | 455 | 428.5 | 26.5 | 22 | 1.20 |
| Pink 981 #6 Whiteboy | 370.5 | 331.5 | 39 | 17 | 2.29 |
| Y1339 #7 | 405.5 | 384.5 | 21 | 15 | 1.40 |
| Pink CT 549 #8 Joe | 362 | 325.5 | 36.5 | 15 | 2.43 |
| Y1299 #9 Markboy | 314.5 | 280.5 | 34 | 16 | 2.13 |
| Orange CT 842 #10 | 344.5 | 293.5 | 51 | 14 | 3.64 |
| Purple 808 #11 | 337.5 | - | - | - | - |
| Red 347 #12 | 313.5 | - | - | - | - |

2) 鸣叫声功能
研究方法：研究人员利用水听器记录了8只抓捕个体的5种主要鸣叫声类型（借助信标频率可区分阵列内的不同个体）。1999年野外工作结束后，研究团队将通过相关分析，探究在三次野外考察季中采集的雄性个体鸣叫声是否携带其生理特征（通过健康状况或“质量”评估）相关信息。目前该研究子课题的总样本量为13只雄性个体（1997与1998年数据）。
现有研究结果愈发表明，仅由雄性发出的长颤音（Long Trill）可能在吸引雌性与挑战竞争对手中发挥关键作用。研究团队开展了两项回放实验，以探究该重要鸣叫声及其他雄性鸣叫声的功能。
第一项实验始于1997年，按照系统实验流程，观测了8只监测雄性与1只雌性对各类主要鸣叫声及对照声音（海象鸣叫声）的反应。针对雌雄个体，研究人员可借助信标阵列记录其相对于水下扬声器的位置变化，利用DAT录音机与水听器记录其鸣叫声行为，通过三台水下摄像机记录其在回放扬声器附近的活动，并监测特定个体的游泳速度与心率。目前该研究子课题的总样本量为13只雄性与2只雌性个体（1997与1998年数据）。
第二项实验同样始于1997年，更直接地探究了雄性间竞争与跨性别的鸣叫声功能。前期试点研究显示，雄性会主动用自身的长颤音重叠竞争对手的长颤音鸣唱，这一行为与领地鸣禽类似。研究团队开展了“交互式”回放实验，以探究重叠竞争对手长颤音鸣叫声的影响。研究人员通过实时野外声谱仪（"real time" field spectrograph）识别特定定居雄性的连续5次长颤音鸣叫声，随后以三种方式播放：(1) 完全重叠、(2) 部分重叠，或(3) 先用陌生雄性的长颤音鸣叫声先行播放。通过MiniDisc播放器按照系统流程将鸣叫声播放给不同的定居雄性。随后利用水下摄像机、信标阵列与水听器记录4只雄性与5只雌性的冰下移动模式变化及鸣叫声反应。目前该研究子课题的总样本量为7只雄性与8只雌性个体（1997与1998年数据）。
此外，研究团队通过连接固定摄像机与水听器的延时录像机，采集了特特尔岩区域主冰裂缝沿线雌雄威德尔海豹的连续声像样本。

3) 父权分析：样本采集
研究方法：通过实验室分析皮肤样本（直径6mm）以确定特特尔岩区域雄性的交配成功率。1997与1998年，研究人员从所有雄性、雌性及幼崽的后鳍肢趾间蹼边缘采集皮肤样本，使用皮革冲头获取样本，样本将存储于装有100%乙醇的离心管中，该存储方式可最大限度减少样本降解。目前相关分析尚未开展。本季研究测试了一种新型采样技术：利用安装在杆端的小型活检冲头，但该技术效果不佳，活检头仅采样2-3只个体后便会变钝。不过剪取技术效果极佳，经验丰富的采样人员操作时，被采样个体有时甚至不会苏醒。

### 重要研究发现
本研究首年的部分成果已于去年8月在基督城举办的SCAR会议上展示，相关摘要发表于《新西兰自然科学》系列期刊。
Harcourt, R.G.、Hindell, M.A.与Waas, J.R.，1998。繁殖季自由活动威德尔海豹的冰下移动与领地利用。《新西兰自然科学》23: 72-73
本研究最有趣的发现之一涉及三维潜水剖面的解读。一篇关于自由活动威德尔海豹三维潜水剖面的论文已接近完成。其他拟发表的论文包括潜水期间心率测量、雌性觅食行为、交流与领地行为，以及核心繁殖相关研究的论文。