1 Is there a social hi erarchy in the heifer herd of Finca Paraso? Kai Patterson Department of Ecology and Evolutionary Biology University California, Santa Cruz UCEAP Tropical Biology and Conservation Spring 2019 7 June 2019 A BSTRACT Dairy cows were domesticated about 10,500 years ago and have been used for milk production ever since. In Costa Rica, they usually live in herds in pastures, therefore they spend most of their time near each other. Research shows they have hierarchies which can be influenced by size, age, and lactation cycle. In this study, I set out to find the social hierarchy in a herd of heifers who are of similar age and size, and do not have a lacta tion cycle. I traveled to La Finca Paraso to observe heifers for a total of 12 hours, and recorded every time a heifer gave or received an aggressive or affectionate act. I recorded the order the heifers traveled from one pasture to a new pasture, and twi ce a day, I recorded the spacing of each heifer in relation to the other individual heifers. The data did not support a strong social hierarchy in the herd. There are many factors that could have influenced the lack of social hierarchy in the herd: change in heifer composition of the herd, time of observation, or time heifers spent laying/resting. Existe una jerarqua social en el grupo de novillas en la Finca Paraso? R ESUMEN Las vacas lecheras fueron domesticadas hace unos 10 500 aos y desde entonces se siguen utilizando para la produccin de leche. En Costa Rica, generalmente se mantienen en manadas en los pastizales y por lo tanto pasan la mayor parte del tiempo en grupo cercano. Investigaciones han demostrado que pueden presentar comportamiento de jer arquas que pueden ser influenciadas por el tamao, la edad y el ciclo de lactancia. En este estudio, me propuse estudiar si existe una jerarqua social en una manada de novillas de edad y tamao similares y sin ciclo de lactancia. Observ el grupo de novi llas en La Finca Paraso durante 12 horas y registr cada vez que una novilla daba o reciba un acto agresivo o carioso. Registr el orden en que las novillas caminaron de un pastizal a otro y, dos veces al da, registr la distancia entre cada novilla en relacin con las otras novillas individuales. Conclu que no existe una jerarqua social fuerte en el grupo de novillas. Hay otros factores que pueden influir en la falta de jerarqua social: el cambio en la composicin del grupo, las horas de observacin y el tiempo que las novillas pasaron descansando.
Social hierarchy in heifer herd? Patterson 2 Social interactions and organization is present in many groupings of animals, whether it be a school, flock, pack, or a herd (Barr, Dickson, & Wieckert 1967). In the wild, there are many examples of soci al hierarchies in animal groups. In invertebrates, the most widespread known hierarchy are bee colonies. This hierarchy is comprised of a queen, female workers, and drones. In the realm of vertebrates, there are strong hierarchies in meerkats where different meerkat members have different jobs and ranks (Madden, et al. , 2009). Even in pigeon flocks, the hierarchy of the group determines the direction the of flight for the entire flock (Nagy, et al ., 2010). Hierarchies can determine much of the behavior of t he members of the group, whether the animals are wild or domesticated. Cows were domesticated from wild ox by humans around 10,500 years ago (University College London 2012) and they can be found in herds, much like other wild large herbivorous mammals. T hey lack predatory morphological features such as claws and sharp canine teeth; instead they have hooves, keratinized body parts used for balance, and molars for chewing cud. Cows are ruminants, so they eat grasses which is chewed, stored in on e of their s tomachs, and then regurgitated as cud to be chewed more at a later time. A 1999 study focused on the impact of different types of stalls on the cowâ€™s overall wellbeing ; this study found the type of stall directly and significantly impacts the comfort and b ehavior of the cow (Haley & Rusheen 1999). Research has also been done on how regulation of automatic feeders can enhance the cowâ€™s welfare by decreasing wait times in the feeding stalls (Oberschtzl Kopp 2016). Both of these studies support the notion that cows are complex organisms that have specific needs and are influenced significantly by their environment. Cows have a more complex intelligence that can be seen in many ways; one being their behavioral changes with environmental comforts, and another b eing the behavioral interactions they have with each other. There have been many studies focusing on the factors influencing milk production because of the economical purposes of dairy cows. There have been a lower frequency of publications focusing on cow behavior compared to production (Ruehl 2012). Within this small niche of studies on cow behavior, the focus is mainly on post pregnancy cows, and not so much on heifers, which are cattle that have not lactated before. One study concluded milking order and dairy production had no significant correlation (Fohrmand & Shein 1955). It also concluded that there is a highly significant relationship between rank and age, and also rank and weight (Fohrmand & Shein 1955). This could mean when the heifers grow older and become cows, their rank could possibly be predicted by their age and/or weight. By focusing on heifers, I will be able to exclude factors such as milk production or lactation cycles (Soffie 1976). There are studies that have concluded that cows have complex behaviors and domesticated temperaments that arose through artificial selection (Fordyce 1984, Haskell 2014) . The impacts of calf separation from the mother cow have also been studied; it concluded the immediate impacts of separation are stronger the longer the calf and mother are kept together (Flower & Weary 2003). Being with the mother allows the calf a better foundation, which improved the health, weight gain, and future productivity of the calf (Flower & Wear y 2003). This supports the prediction that heifers have different upbringings that have influenced their foundation, therefore influenced their hierarchy. The heifers in this study have been bought from different farms , but were all separated from their mothers within a few days after birth. They are all near two years old, around 500
Social hierarchy in heifer herd? Patterson 3 kilograms, and have not been pregnant or lactated before. The heifers are either the Jersey breed or a hybrid breed of Holstein and Jersey, therefore they are all around the same weight and size. This study asks the question: Is there a social hierarchy in the heifer herd of La Finca Paraso? I hypothesize there will be a social hierarchy in the heifer herd at La Finca Paraso. I predict more aggressive heifers and heifers i n the front of the pasture line are higher in the hierarchy. I also predict heifers that are more affectionate/less aggressive and towards the end of the pasture line are more submissive in the herdâ€™s hierarchy . MATERIALS AND METHODS I made four visits to Finca Paraso, which is located in Los Tornos, Costa Rica. I observed eight heifers over a two week period for a total of 12 hours of observations. To study the possible presence and structure of hierarchy between these heifers, I analyzed their behavior in three parts: interactions between individuals, physical spacing between them, and the order of heifers when moving between pastures. I observed interactions and spacing on the tenth, thirteenth, fifteenth, and sixteenth of May 2019. I recorded pasture order on the tenth and twelfth of May 2019. The site is a small farm that has eight heifers, who are moved every few days depending on the pasture quality. There were originally nine heifers, but one was sold two days before this study. The heifer sold was the largest and most aggressive one of the herd. There are over 25 pastures that the heifers are circulated through. The weather was typically breezy and sunny and around 21 degrees Celsius. Only one day had rain, and it occurred in only the second half of the day. To study the interactions between each heifer , I counted the number of aggressive and affectionate actions. Affectionate actions include nuzzling, grooming, and licking. Nuzzling is when a heifer would rub its head on another heifer without much force. Grooming is extensive licking of hair of another heifer, and similarly licking is when the heifer contacts another heifer with her tongue for any length of time. Aggressive acts include kicking, charging, and headbutting. Kicking is forceful contac t by one heifer to another via her leg. Charging is when a heifer runs with a high velocity towards another heifer without making contact with the other. Headbutting is when a heifer slams her head into another heifer with force. To study the possibility of heifers having affinities or rivalries with each other, I observed the heifers and classified their placement relative to each other heifer as â€œcloseâ€, â€œnearâ€, â€œfarâ€, or â€œvery farâ€. The spacing was determined by my best estimation. The â€œcloseâ€ category is defined as the heifers are almost touching. â€œNearâ€ is when the heifers were about one body length away from each other (around 2.5 meters). â€œFarâ€ is classified as more than 2.5 meters from each other but still on the same half of the pasture. â€œVery farâ€ is when heifers were more than half the length of the pasture away from each other. R ESULTS There were more aggressive acts than affectionate acts between the eight heifers throughout this study. There was a total of fourteen aggressive interactions and nine affectionate interactions (Fig. 1 and, Fig. 2). Heifers were assigned a letter as identification. Heifer E had zero giving or receiving acts in both the affectionate and aggressive categories. Heifer F had zero aggressive interactions. Heifer A gave th e most affectionate acts, while Heifer B received the
Social hierarchy in heifer herd? Patterson 4 most affectionate acts. Heifer G gave the most aggressive acts, and Heifer H received the most ag gressive acts. Each heifer had an average of 1.125 affectionate acts and 1.625 aggressive acts given and received. Table 1 and table 2 show there was low occurrence of heifers being â€œcloseâ€ or â€œvery farâ€ from each other. The heifers were more likely to be â€œnearâ€ or â€œfarâ€ from each other. When analyzing the order of heifers during pasture changes, Heifer I was first both times and Heifer B was second both times. There was no definitive order to the rest of the heifers (Table 3). Fig. 1. The number of affectionate actions given and received by each heifer. Each letter represents a different heifer. The dar k grey bars represent the number of given affectionate actions and the light grey bars represent the affectionate actions received. 0 1 2 3 4 5 6 A B C D E F G HNumber of OccurrencesHeifer Identification Giving Receiving
Social hierarchy in heifer herd? Patterson 5 Fig. 2. The number of aggressive actions given and received by each heifer. Each letter represents a different heifer. The dark grey bars represent the number of given aggressive actions and the light grey bars represent the aggressive actions received. Table 1 : Frequency of physical spacing between each heifer combination. The top right section is the â€œcloseâ€ category and the bottom left section is the â€œnearâ€ category. The table is organized using a blue grey color spectrum explained in the symbology; lighter colors signify less occurrences, and darker colors signify more occurrences. The striped boxes represent where a he ifer crosses with itself in the table, therefore it is â€œnot applicableâ€. C B A F G H D E C B A F G H D E 0 1 2 3 4 5 6 A B C D E F G HNumber of OccurrencesHeifer Identification Giving Receiving
Social hierarchy in heifer herd? Patterson 6 Symbology Number of Occurrences Color 0 1 2 3 4 5 6 7 N/A Table 2 : The frequency of spacing between each heifer combination. The top right section is the â€œfarâ€ category and the bottom left category is the â€œvery farâ€ category. The table is organized using a blue grey color spectrum explained in the symbology; lighter colors signify less occurrences, and darker colors signify more occurrences. The striped boxes represent where a heifer crosses with itself in the table, therefore it is â€œnot ap plicableâ€. C B A F G H D E C B A F G H D E
Social hierarchy in heifer herd? Patterson 7 Table 3 . The order the heifers traveled to the new pastures on two different days. The heifers are each assigned a letter. The bolded letters signify the heifers that are in the same order for both trials. Each trial is a different day the heifers were observed. 1. 2. 3. 4. 5. 6. 7. 8. 9. Trial 1 I B F H C A G D E Trial 2 I B G F D E A H C D ISCUSSION The results presented do not support my original hypothesis of a social hierarchy in the herd of heifers at La Finca Paraso. The data collected had no strong indication of specific dominant and/or submissive heifers. The heifers tended to stay â€œfarâ€ apart or â€œnearâ€ to each other in the pasture most of the time. The pastures were large enough that the heifers are not forced to be close to each other and could be far enough to be comfortable. The heifers had the choice to be very far from each other, but their tendency to be â€œnearâ€ or only â€œfarâ€ from each other demonstrates they are social herd animals. Although they tended to be in proximity of each other, there was no evidence of a rivalry or aggressive tendencies between any specific he ifers. Most interactions happened during a grazing period, but much of the time, the heifers were laying on the ground. Heifers have a strong motivation to rest, and the longer they are deprived of rest, the longer they will rest (Jensen et al. , 2004). This may explain why some days certain heifers were resting for much longer and for more frequent periods of time. Dairy cows have been bred over time to have more and more milk production with each generation, so cows in general have evolved to rest more be cause their production of milk requires much of their energy (Grant 2004). Because of this rest time, many of the trials recorded were labeled â€œno interactionsâ€. The heifers spent a surprisingly low amount of time grazing during the periods of time I obse rved them . This observation is typical of cows and heifers; they eat much of the day but spend most of their time resting (Friend & Polan 1974). Heifers and cows tend to be much more aggressive during grazing periods (Hansen and Pallesen 1998). This would explain the low number of interactions during my observations. As said before, they spend most of their waking hours resting, therefore they would not interact as often, given the fact they interact mostly when they graze. This result of low interactions would support the idea that these heifers are either not very aggressive, or they are more aggressive during the times I did not observe them when they may graze more. It is also possible the heifers were not as aggressive because of their size. There is a link between the heifers rank and age, and also their rank and weight (Fohrmand & Shein 1955) . I t is possible the lack of differences in age and size means the heifers lack a strong social hierarchy at this point in their lives. The heifers were also eith er Jerseys or Jersey/Holstein mix
Social hierarchy in heifer herd? Patterson 8 breeds, which are similar in size and temperament. This could help explain why the heifers were not very aggressive ; these breeds are not usually aggressive. I predicted the most aggressive heifer would be first in the p asture order, thus supporting a pattern of hierarchy. The pasture order showed there were two leader heifers when changing pastures, but their leading positions did not positively correlate with the number of aggressive acts done by either of these heifers. Partway through the study, there was a Simmental breed heifer that was sold. She was the largest and most aggressive in the group, and her sudden absence may have influenced the herdâ€™s dynamic in the following days. When there is a disturbance in the c omposition of the herd, it can take five to 15 days after the group change to become stable again (Boe and Faerevik, 2003). This heifer in particular could have had a much higher influence on the rest of the herd because of her more aggressive temperament. This could explain why there was no significant pattern in a social hierarchy of the herd I observed. At the time I observed the herd, there was a higher number of aggressive acts than affectionate acts. Social stability is defined as when â€œnonphysical a gnostic interactionsâ€ dominate among the cows in the herd (Kondo and Hurnik, 1990). There was variation throughout the different days I visited, so this herd would not have achieved social stability at the time of observation. Overall, these factors (time spent grazing, time of observation, and change in herd composition) could have influenced the lack of evidence of a social hierarchy in this herd. If a longer study was an option, the herd could be analyzed after the five to 15 day period of restabilizat ion to see if there is a social hierarchy. A CKNOWLEDGEMENTS I would like to thank Emi Triana for all of her help and guidance with my project. She helped me overcome all the obstacles that arose during my study. I would also like to thank the owner of La Finca Paraso, Orlando Vargas Castro and his son Orlando Vargas Vindas. They allowed me to utilize their property for my scientific research and were a huge help when I had questions about the heifersâ€™ behaviors and histories. I would also like to thank F ederico Chinchilla and Frank Joyce, who were always willing to help, even into the late nights. Lastly, I would like to thank the heifers of the farm for letting me watch them for hours. LITERATURE CITED Boe, K. E., and G. Faerevik. 2003. Grouping and social preferences in calves, heifers, and cows. Appl. Anim. Behav. Sci. 80:175190. Flower, F.C. & Weary, Daniel. 2003. Effects of early separation on the dairy cow and calf. Animal Welfare. 12. 339348. Fordyce, G., and M. E. Goddard. 1984. Maternal influence on the temperament of Bos indicus cross cows. Proc. Aust. Soc. Anim. Prod. Vol. 15. Friend, T.H., Polan C.E. 1974. Social Rank, Feeding Behavior, and Free Stall Utilization by Dairy Cattleâ€ Journal of Dairy Science. Vol 57. Grant, R. J. 2003. Taking advantage of dairy cow behavior: Cost of ignoring time
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