Ethogram of Yangtze finless porpoise calves (Neophocaena phocaenoides asiaeorientalis)

XIAN Yi-Jie, WANG Ke-Xiong, JIANG Wen-Hua, ZHENG Bang-You, WANG Ding,*

(1. Institute of Hydrobiology, the Chinese Academy of Sciences, Wuhan 430072, China; 2. Graduate University of the Chinese Academy of Sciences, Beijing 100049, China; 3. Tongling Freshwater Porpoise National Nature Reserve, Tongling 244161, China)

Ethogram of Yangtze finless porpoise calves (Neophocaena phocaenoides asiaeorientalis)

XIAN Yi-Jie1,2, WANG Ke-Xiong1, JIANG Wen-Hua3, ZHENG Bang-You3, WANG Ding1,*

(1.Institute of Hydrobiology, the Chinese Academy of Sciences, Wuhan430072,China;2. Graduate University of the Chinese Academy of Sciences, Beijing100049,China;3.Tongling Freshwater Porpoise National Nature Reserve, Tongling244161,China)

Underwater behavioral patterns of one Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) calf in captivity and those performed on the water surface by two calves in semi-natural environment were focally followed and continuously recorded until one year postpartum to construct the ethogram. The results indicate that 1) the three calves could display diverse and active behavioral patterns; 2) soon after birth, patterns critical for survival appeared first; 3) playful and social patterns predominated the ethogram; 4) most of the patterns were alike across age classes; 5) most of the patterns appeared at the calves’ early life stage. It is possible that the above characteristics are adaptively shaped by the aquatic and social life of this subspecies.

Neophocaena phocaenoides asiaeorientalis; Calf; Behavioral pattern; Aquatic environment

For ethological studies, particularly species-oriented ones, clear, concise and comprehensive description of characteristic behaviors, i.e. the construction of ethograms, is fundamental (Brown, 1975; Lehner, 1996). In this sense, behavioral observations across all age-sex classes under different environments are needed so that understanding of Tinbergen’s (1963) four questions about behavior (function, causation, ontogeny and evolution) can be illuminated by inter- and intra-species comparisons. In the field of animal conservation and welfare, an operational ethogram can be used to evaluate the achievement of our efforts (Banks, 1982; Gonyou, 1994; Jiang, 1997).

As one of the most modified mammals, cetaceans have evolved to assume many behavioral patterns greatly different from their terrestrial counterparts to adapt to the aquatic environment (Clutton-Brock & Wilson, 2002). For a long time, these fascinating patterns havestimulated our interest and have been profusely documented — examples include spy hop, tail lift and breach in bottlenose dolphins (Tursiops truncatus) (Müller et al, 1998) and killer whales (Orcinus orca) (reviewed in Heyning & Dahlheim, 1988). In previous studies, although calves have been included, systematic descriptions of their behavioral patterns are scarce, with exceptions such as Mann & Smuts (1999) for bottlenose dolphins (Tursiopssp.) and Miles & Herzing (2003) for Atlantic spotted dolphins (Stenella frontalis). In general, this situation can be attributed to 1) difficulty in subject availability (Herman & Tavolga, 1980), especially for endangered species; 2) the common problems in cetological research, i.e. the often impossible access to and following of the focal animals in their open and wide habitat for a long period (Mann, 1999) and 3) researcher’s interest (e.g. Gubbins et al, 1999).

According to Barnard (2004), young animals can display diverse behavioral patterns especially in playful context. In cetacean calves, these include swimming, socio-sexual interaction, object manipulation and investigation etc., which may have adaptive significance in refining their motor, foraging, social and reproductive skills for present and future life (Herman & Tavolga, 1980; Mann & Smuts, 1999; Mann, 2006). Therefore, to study cetacean calves’ behavioral patterns on one hand may further our understanding of this mammal’s adaptations to their aquatic environment. On the other hand, this work may help us to trace the components of adult behavioral patterns back to those in childhood, so that maturation of the patterns together with their underlying mechanisms can be revealed (Herman & Tavolga, 1980; Mann, 2006).

The Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) is one of the smallest toothed whales, only distributed in the middle and lower reaches of the Yangtze River and its main tributaries (Gao & Zhou, 1995). As a victim of intensive human activities, their population size has dramatically decreased from around 2700 in the early 1990s (Zhang et al, 1993) to 1800 in 2006 (Zhao et al, 2008). According to IUCN criteria, their protective status is recommended to being upgraded from “Endangered” (Baillie & Groombridge, 1996) to “Critically Endangered” (Zhao, 2009).

To protect this subspecies, several captive facilities and semi-natural reserves have been established since the late 1980s. Under these circumstances, individual identification and long term behavioral observation on this small-sized, timid- and elusive-tempered (Jefferson & Huang, 2004) and turbid-water living cetacean become possible (e.g. Jiang, 2000; Xiao & Wang, 2005). With calves introduced into captivity and born in semi-natural reserves, several descriptions on their behavioral patterns have been carried out (e.g. Hua et al, 1993; Yang & Chen, 1996; Wang, 1998; Wei et al, 2002; Jiang & Yu, 2006). However, the studies defined the patterns broadly and their observational periods were relatively short. In the present study, we longitudinally followed the underwater behavioral patterns of one captive-born calf during the first year postpartum. In addition, patterns performed on the water surface by two semi-natural born calves were also followed until one year postpartum. Based on these efforts, an ethogram including the day age when each pattern was first observed was constructed and functions of the patterns were discussed.

1 Material and Methods

1.1 Subjects and housing management

The first subject was the world’s first captive-born calf of Yangtze finless porpoise in Baiji Dolphinarium, Wuhan, Hubei Province, China, born on July 5 2005 and called Terry (Wang et al, 2005). He lived with four adults: his parents, one other female and one other male. The housing system of the dolphinarium includes a kidney-shaped pool [20 m×(7 - 8) m×3.5 (depth) m] and a round pool (diameter=10 m, depth=3.5 m), which are connected by an underwater corridor [1.7 m×1.4 m×2 (depth) m]; there are eight rectangular windows (2 m×1.5 m each) on the walls of both pools: seven for the kidney-shaped pool and one for the round pool (Liu, 1997). Through the windows, the animals were observed in the present study. A close-circuit filter system recycles the water four times a day. During the year, the water temperature is controlled between 8 - 30℃ depending on the season.

From March 15, 2005 to March 6, 2006, the underwater corridor was gated by a metal fence. As a result, the mother, the calf and the other adult female were left in the kidney-shaped pool, while both adult males (including the father of Terry) were housed in the round pool. This practice was necessary when considering the adult males’ potential abuse on the mother and calf. Fish (mainly crucian carps,Carassius auratus) was provided for the adults during the four regular feedings at 8:30 - 9:00, 11:30 - 12:00, 14:30 -15:00 and 16:50 - 17:20 each day (about 1 kg/meal for each individual). To fulfill the nutritional requirement of the mother, an extra meal was supplied at 20:00 - 20:30 from winter 2004 to spring 2006. When Terry started to ingest fish at 98 d of age, he was fed in accordance to his mother’s schedule. For other information of Terry and the housing management, see Xian et al (2010).

The second and third subjects were C06 (male) and C07 (sex unknown) born to different mothers in July 13, 2006 and August 13, 2007 respectively in the semi-natural water of Tongling Freshwater Porpoise National Nature Reserve, Tongling, Anhui Province, China. The two calves lived with another four to five individuals including the parents. C06 died from an accident on his 109 d postpartum. The semi-natural water is a former side channel (30°48′-30°49′N, 117°43′ - 117°44′E) of Yangtze River and has been completely enclosed by Heyue Islet and Tieban Islet since the end of 1993. Now, the channel is about 1 600 m long and 80 - 220 m wide with flat and sandy bed. In drought season, water is pumped in from the Yangtze River. During the study, the water level of the deepest area fluctuated between 4 - 5 m, and the temperature 0.3 m under the water surface changed between 0 - 38°C. Although the porpoises can forage in the channel, they are still fed with fish (mainlyCarassiussp.,Cyprinussp.,Hypophthalmichthyssp. andCtenopharyngodonsp.). Feeding is regularly conducted at 9:00 - 9:30 and 14:00 -14:30 each day, with about 2 kg/meal provided for each individual except the calves. In contrary to C06 which was not observed to feed on fish throughout his 109 d of life, C07 started to feed at 87 d postpartum and fish was provided for it since then until the end of the study.

1.2 Sampling and recording methods

In captivity, focal following and continuous recording methods (Martin & Bateson, 1993; Lehner, 1996) were used to study Terry’s underwater behavioral patterns. Before 3.5 d of age, the patterns were recorded on the data sheet day and night. After that until 364 d postpartum, the patterns were video-recorded according to the following design. On each Sunday and Wednesday, during the whole daytime, a recording session lasting 10.5 min was randomly selected from each natural hour. The video-recording was carried out near the underwater windows by an observer equipped with a Sony?DCR-VX1000E digital video camera. Given the potential disturbance of human activities on the animals’ behaviors, some recordings should be conducted 20 min before or after the feeding.

Produced by a Panasonic?NV-DV2000 digital video cassette recorder and the software of 10 Moons?DV 1-2-3, all the videos recorded in captivity were real-time transformed into mpeg 2 format and stored in the hard disk. Videos were manually played back with speed 4 times faster than the real-time. When a new behavioral pattern was detected, the video was paused and then played frame by frame to record the pattern together with the day age. For other information of the sampling and recording methods, see Xian et al (2010).

At the channel in Tongling, the focal following and continuous recording methods were also adopted. In the day time, behavioral patterns performed on the water surface by C06 and C07 were visually observed. For C06, observations were carried out everyday from birth to 18 d postpartum, every other day from 19 - 76 d and every 2 - 3 d from 77 - 109 d; for C07, observations were conducted everyday from birth to 30 d of age, every other day from 31 - 62 d, every 2 - 3 d from 63 - 255 d and every 7 d from 256 to 364 d. During each working day, an observational session lasting 2 h was selected from dawn to 8:30, 10:00 - 13:30 and 15:00 to dusk respectively. A data sheet was used to record each new behavioral pattern of the two calves together with the day age. During the study, the observer who was situated on the channel bank as high as 6 m, closely followed the focal individual. Naked eyes and a pair of Fujinon?binoculars (7 × 50 mm) were alternatively used according to the distance between the animal and observer. Generally, the distance was kept between 30 -200 m, a tradeoff between minimizing the observer’s potential disturbance on the animal’s behaviors and observational reliability.

1.3 Ethogram construction

We referenced to the description and terminology used in bottlenose dolphins (Müller et al, 1998; Mann & Smuts, 1999) and captive Yangtze finless porpoises (Xiao & Wang, 2005) but made substantial modifications in the present study. For the sake of objectivity, functional description of the behavioral pattern was avoided unless there was evidence to support it (reviewed in Lehner, 1996). According to the context and main body part involved (Müller et al, 1998), all the behavioral patterns were classified to construct the ethogram, in which the day age when each behavioral pattern was first observed was noted.

2 Results

In captivity, during Terry’s first 3.5 d postpartum, the total sampling time was 84 h. From 3.5 to 364 d postpartum, 99 working days led to 181.9 h of videos (1.8 ± 0.5) h/d. In the channel, from birth to 109 d of life for C06, during 49 d of observation, the sampling time amounted to 284.9 h (5.8 ± 0.8) h/d; for C07, from its birth to 364 d postpartum, during 114 d of observation, the hour count was 656.2 h (5.8 ± 0.8) h/d.

In sum, 49 behavioral patterns were described in captivity, 50 in the channel, among which 38 were shared by both calves, and 5 and 7 were exclusively recorded for C06 and C07, respectively. All of the patterns were classified into 11 categories to construct the ethogram (Tab. 1).

Tab. 1 Ethogram of the calves based on observations underwater or on the surface

Observed age (d) Category Behavioral pattern Description Terry C06 C07 Follow Swim behind and towards another progressing individual far away from the latter’s one body length 1 1 1 Approach Swim into the radius of one body length of another individual which keeps relatively still 1 11 9 Leave Swim out of the radius of one body length of another individual which keeps relatively still 1 11 16 Group Aggregate with another or other individual(s) while the distance between any of them is within two body length of adults 1 1 1 Sexual play Arch the genital region towards the counterpart of another individual. Sometimes penis erection, intromission and thrust can be observed 33 Decline Lift the fore-section vertically or obliquely, and forward clear the surface until submergence 70 18 Stiff lunge Extend the long axis straightly, thrust into the air completely in vertical or oblique gesture and retreat along the original routine smoothly or slap the surface with the belly noisily 17 2 Breach Lift the fore-section obliquely in lateral or ventral position and land noisily on the water surface with the side 62 19 Aerial behavior Bow Thrust into the air in dorsal position and assume an apparent arch at the peak. In descent, the peduncle remains relatively stationary or moves upward as the fore-section falls down. Distance between the start and re-entry points is within one body length 30 12 Leap Thrust into the air in dorsal position and assume a slight arch at the peak, resulting in clean or noisy dropdown. Distance between the start and re-entry points is more than one body length 20 12 Porpoise Thrust into the air in dorsal or lateral position with the peduncle arched down the water surface, resulting in noisy dropdown. Distance between the start and re-entry points is more than one body length 70 18 Sink Fall down to the ground without any movement 152 Circle fall Fall down freely with head first, circling round a supposed column 138 Stationary behavior Float Keep still on the surface while the head and/or tail can bend down or expose out of water 19 50 9 Hang Stay vertically in the water column, sometimes with head touching the surface slightly 103 Lie Stay motionless on the ground in dorsal position 208 Arch Bend the head and/or tail to form arch, concave or “S” shape 19 Bubble manipulate Expel bubbles from the mouth or blowhole 75 Ring manipulate Expel rings from the mouth 138 Object manipulate Chase, spit, lift or bite small fish, feces piece, plants, etc. 33 32 58 Mouth movement Spit Shoot a thin water stream into the air while floating or being underwater 51 24 92 Mouth open Open the upper and lower jaw in non-feeding occasion 51 72 Mouth jerk open and shut the upper and lower jaw repeatedly 76 Suckle Attach the lip on the mother’s teat tightly 1 Ingest Swallow fish directly 98 87 Head movement Head thrust Rush the head out of water vertically, slapping the jaw on the surface noisily when falling down 1 1 Head lift Expose the head vertically or obliquely out of water, keeping motionless or scanning around 12 141

Observed age (d) Category Behavioral pattern Description Terry C06 C07 Head jerk Move the head inward and outward, or from side to side 33 56 77 Head bump Bump the head onto the surface of another individual or object 1 83 4 Spy hop Lift the fore-section vertically out of water and then retreat along the original routine with the flipper waving sometimes 53 48 16 Chin slap Raise the head in dorsal position and strike against the surface noisily 1 66 Vibrate Expose and retreat the trunk continuously 337 252 Trunk movement Tumble Revolve the body in the column with the body center as the pivot 75 Roll Revolve around the long axis continuously 33 12 62 Over turn Turn from side to side 22 4 Tail lift Expose the tail vertically or obliquely out of water with the fluke curled sometimes 40 32 Tail wave Move the tail up and down or sideways 64 1 Tail movement Tail slap Strike the tail on the surface noisily, resulting in progress 95 85 Tail concave Bend the tail backwards 33 Twist Curl the tail on the counterpart of another individual while swimming under it 26 Defecate Expel feces Others Erect Expose the penis 1 37

3 Discussion

According to Chen et al (1992), behavioral patterns of the finless porpoise are dull. In the present study, however, the three calves could perform diverse and active patterns underwater or on the surface, such as Rush, Ring, Leap and Spit. In previous studies, researchers have recorded as many as 40 patterns in juveniles, sub-adults and/or adults of the Yangtze finless porpoise (Hua et al, 1993; Wang, 1998; Xiao & Wang, 2005). Hence, the behavioral description made by Chen et al (1992) is not appropriate for this subspecies.

In our ethogram, there are 8 behavioral patterns (Respire, Move, Echelon position swim, Infant position swim, Surface, Synchronous surface, Delayed surface and Dive) observed for the three calves during their first day of life. In the animal kingdom, although behavioral development varies across species, it is predicted that behavioral patterns critical for survival should appear earliest in life (reviewed in Barnard, 2004). Different from the young of many terrestrial mammals such as rodents and carnivores, to survive in their aquatic environment, cetacean calves should be able to respire, swim, surface and dive soon after parturition. During the phylogenetic process, they have evolved to take on precocious locomotion, buoyant physical form and close mother-calf bond (Tavolga & Essapian, 1957; Cockroft & Ross, 1990; Mann & Smuts, 1999). In this way, the calves in the present study could quickly acquire the above patterns soon after birth.

During the three calves’ first day of life, besides the above survival-critical patterns, some playful and social patterns such as Touch, Rub, Follow and Group were also observed. Throughout the whole study period, many of the calves’ patterns were playful and social — as seen in many other young mammals (Barnard, 2004) including bottlenose dolphins (Gurevich, 1977). For toothed whales which should move continuously in water and live a complex social life (Connor et al, 1998), the development of diverse playful and social patterns in childhood may help them to enhance neuromuscular competency, practice adult patterns, generate novel patterns and negotiate social relations (Barnard, 2004). Take “Object manipulate” in the present study for example, no matter what the underlying motivation was, this pattern might be important for the calves’ subsequent maturation of feeding/foraging behavior as seen in bottlenose dolphins (Mann & Smuts, 1999).

Despite the great difference in observational period between C06 and C07 (109 vs. 365 d), their numbers of behavioral patterns are comparable (43 vs. 45, with 38 shared). Moreover, most of their patterns have been alike those in other age classes of the Yangtze finless porpoise (Hua et al, 1993). Similarly, most of Terry’s patterns have also been alike those in the sub-adults and adults (Wang, 1998; Xiao & Wang, 2005). For the three calves, a large amount of patterns appeared at their early life stage. It is possible that these characteristics are related to their quickly improved locomotion abilities. In bottlenose dolphins, the similar situation has also been found (Gurevich, 1977).

From above, we can see that the three calves shared many aspects of behavioral patterns, even though they lived in two different environments. One difference is that C06 and C07 were observed to display vigorous aerial patterns such as Breach, Bow and Leap, but it is not for Terry. In other age classes of this subspecies in captivity and the channel in Tongling, a similar difference has also been noted (Xiao & Wang, 2005; personal observation). It is likely that release of the aerial patterns has been suppressed in captivity with limited space, hard wall, etc. From the perspective of adaptation, the suppression of aerial patterns in captivity might protect the calf from accidental injuries and stranding.

Although our findings are only from three calves in captive and semi-natural environments, this work further enriches our knowledge about behavioral biology of the Yangtze finless porpoise. Moreover, it gives implications in management and conservation of this subspecies, e.g. environmental enrichment is needed to fully release the calves’ behavioral patterns particularly at their early life stage. Since behavioral development is an ongoing process (Barnard, 2004), to closely follow the change of the patterns over a long period is needed in the future.

Acknowledgements:Our colleagues were dedicated to animal husbandry, among whom Lijun DONG, Xinqiao ZHANG and Shouyue DONG helped tremendously with video recording, and Wuyi WANG and Bajin ZHANG greatly assisted in the field work. Jiakuan SHU, postgraduate of School of Life Science of Anhui University, shared with us his experience and information at the channel. Kai ZHANG, postgraduate of School of Geography and the Environment, University of Oxford, provided careful revisions on the manuscript. Anonymous referee(s) made helpful comments and suggestions on the improvement of the manuscript. We extend our grateful thanks to all of them.

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幼年長(zhǎng)江江豚的行為譜

先義杰1,2, 王克雄1, 蔣文華3, 鄭邦友3, 王 丁1,*

（1. 中國(guó)科學(xué)院水生生物研究所，湖北 武漢 430072；2. 中國(guó)科學(xué)院研究生院，北京 100049；3. 銅陵淡水豚國(guó)家級(jí)自然保護(hù)區(qū)，安徽 銅陵 244161）

采用焦點(diǎn)動(dòng)物跟蹤法及連續(xù)記錄法，觀察了人工飼養(yǎng)條件下一頭幼年長(zhǎng)江江豚（Neophocaena phocaenoides asiaeorientalis）的水下以及半自然條件下兩頭幼豚的水面行為型式。觀察時(shí)間最長(zhǎng)持續(xù)至出生后一年，以構(gòu)建其行為譜。結(jié)果顯示：1) 所有幼豚都能表現(xiàn)出豐富多樣且活躍的行為型式；2) 幼豚剛出生時(shí)，與存活攸關(guān)的行為型式最先出現(xiàn)；3) 具有玩耍和社居性質(zhì)的行為型式在行為譜中占大部分；4) 幼豚大部分行為型式已與其他年齡段個(gè)體的相似；5) 大部分行為型式出現(xiàn)在生命的早期階段。以上特征可能是這種動(dòng)物對(duì)水生和社居生活的適應(yīng)。

長(zhǎng)江江豚；幼豚；行為型式；水生環(huán)境

Q959.841; Q958.14

A

0254-5853-(2010)05-0523-08

2010-02-09；接受日期：2010-06-05

國(guó)家重點(diǎn)基礎(chǔ)研究發(fā)展計(jì)劃（2007CB411600）；國(guó)家自然科學(xué)基金（30730018）；中國(guó)科學(xué)院院長(zhǎng)基金（220103）*

（Corresponding author），Tel: +86-27-68780178; Fax: +86-27-68780123; E-mail: wangd@ihb.ac.cn

10.3724/SP.J.1141.2010.05523

date: 2010-02-09; Accepted date: 2010-06-05

s: National Basic Research Program of China (2007CB411600); National Natural Science Foundation of China (30730018); President Fund of Chinese Academy of Sciences (220103)