Introduction

    This year the W.C.V.M. behaviour group was given the unique opportunity to conduct behavioural observations on cattle in a P.F.R.A.(Prairie Farm Rehabilitation Administration) community pasture setting. The community pasture systems serves as a "summer camp" for cattle, complete with breeding services and daily supervision provided by cowboys and pasture managers. Typically each pasture contains a mix of cattle from various herds exposed to multiple bulls. For ethologists who are studying cattle behaviour, the community pasture situation is rare and it affords us the unique opportunity to study cattle under natural range condition where the cattle have minimum restrictions on their movement and social groupings. In addition, the community pasture system presents unique questions and challenges which are seldom confronted by cattle producers who are tending a single cow/calf herd. This does not mean the questions are not important. In fact, the opposite is true in Saskatchewan where roughly 40% (around 400,000 cows) are sent to community pastures for grazing and breeding each year. The social dynamics, movement patterns and the behavioural questions arising from the community pasture systems are extremely important for the beef industry in Saskatchewan when one considers the large numbers of cattle involved in the community pasture "experience". Several questions immediately surface:

• Should the stocking ratio of bulls to cows in a community pasture system be similar to that followed in a single herd situation (1 bull for every 25-35 cows), since cows in the community pasture may form subgroups representing their natal cow herds?
• Will bulls readily travel to all subgroups or do they remain somewhat territorial or join specific subgroups of cows?
• Are pregnancy rates associated primarily with the body conditions of the cows or does the dynamic social groupings and spatial orientation of the cows and bulls play an important role?
• Do cattle show tendencies to spatially orient and "drift" towards their home location, thereby influencing the forage utilization? Such a spatial orientation could result in a disproportionate area within the range being grazed, while other areas are under utilized. (This is the situation often observed by pasture managers).

Determine the extent to which cattle within a community pasture system form subgroups which are representative of their respective herds or origins.

Determine if cattle show spatial orientation and "drift" towards their home farm.

Progress to Date

Materials and methods:

    The study site was the Rudy-Rosedale Community Pasture, situated approximately 50 Km south of Saskatoon, Saskatchewan. Two groups of cow-calf pairs and breeding bulls were studied between May and October 1996. The first comprised 78 cows and their calves from 6 patron herds exposed to 2 Limousin bulls. These were grazed initially on 65 ha of improved pasture and were later moved to a 260 ha field. The second group was composed of 126 cow-calf pairs from 4 patron herds and was exposed to 4 Charolais bulls. This group first occupied 500 ha of native pasture and was later moved to an area of about 1090 ha.
 

Relationship between conception rates and body condition scores

    Immediately before and after the grazing season, subjective condition scores were recorded for each cow based on manual palpation of back fat. Scoring was from 1 (extremely thin) to 5 (overly fat). Optimum breeding condition was judged to be about 4 or less on this scale. At the end of the grazing season 108 cows were found to be pregnant (85.7%) and we looked to determine whether failure to conceive was associated with poor body condition. Mean condition scores for all cows increased slightly over the grazing season from 3.94 to 4.15. However there was no significant difference in condition scores between pregnant and open cows either before (3.95 and 3.81 ns) or after (4.15 Vs 4.19 ns) the grazing season, though such a relationship has been shown in previous studies. Typically there is a correlation between higher condition scores at the start of a grazing season with higher conception rates. Our findings suggest that given a reasonable standard of nutrition overall, minor differences in body fat reserves are not predictive of ability to conceive. There are undoubtedly other factors worth considering, including the relative ranging behaviour of cows and bulls within the field. Later analysis of data obtained in the summer of 1996 will investigate some of these factors.
 

Social grouping and location preferences during late-season grazing

    This analysis investigates two hypotheses. Firstly that cattle will preferentially associate with members of their own home herd, even after several months of sharing a range with animals from other farms. And secondly, that herd groupings will tend to show a preferences for certain locations within the field.
 

Social group composition

    The area within 200m of the perimeter of the large field was divided into rectangular zones of 600 m (+/-200m) in length. These were defined in relation to features within the field and were thus not all the same size. There were 36 such zones making up the 14 km perimeter of the field. This area was traversed using a combination of walking and motor vehicle on 10 occasions during September and October 1996. Cattle of the 4 patron herds in this field had been colour coded using red, green, yellow or blue ear tags at th e start of the grazing season. Observations consisted of noting the numbers of adult cattle of the 4 herds found in each location on each occasion. In total 706 animal locations were recorded, accounting for about 56% of the cows on each observing day. Only 15 of the 36 available locations were ever seen to be occupied by cattle (this is an ongoing problem in range utilization at this site, which we are also interested in investigating). Where animals were seen, the mean number in a location was 17.5, and animals thus associated in space were regarded as a "group" for the purpose of this study.

    For each herd and each group observed, the likelihood of observing such proportions of animals was calculated as a binomial probability score. Each score was classed as either "extreme" or "non-extreme" according to whether the probability fell within the upper or lower 25% of the probability distribution or within the middle 50%. For example if a group of 15 cows of which 7 were from the red herd was seen, the probability of seeing this many reds or more by coincidence is .309 based upon the total number of reds in the pasture and the total number of cows in the pasture. In other words finding a group of 15 cows in which 7 were from the red group would not be unusual based on probabilities and would not represent proof that the red cattle were clustering together. Such a group would be classed as "non-extreme" as regards the number of reds. On the other hand, if a group with 22 red cows out of a total of 38 was seen, the probability of seeing this many reds or more together would be .008 since it represents nearly all the red cows. This is considered rather unlikely to happen by chance and would be classed as "extreme". For the four herds the frequency of each class was compared for 41 groupings in a 4 X 2 contingency table. The overall chi-square of 14.67 with 3 df is significant at p=0.0021. This is interpreted as suggesting that there is a strong tendency for herdmates to be seen in association with each other rather than in company with members of the other herds.

    We tended to observe a higher number of incidences where a group of cattle was made up of predominantly more cattle from a specific herd than one would expect by random chance. At this point in the analysis it is difficult to tell whether herdmates prefer each others' company, independent of the location, or whether they merely tend to prefer the same locations. However, the casual observation made by cowboys and pasture managers who claim that cattle regroup into natal herds appears to hold true under our scrutiny.
 

Implications of findings:

    These finding could have tremendous implications on the method of determining the proper bull to cow stocking ratios. Instead of trying to meet a specified ratio of bulls to cows, community pasture managers may also need to maintain an adequate number of bulls based on the number of patrons using the pasture and the number of subgroups of cattle which may form. This would be especially true under extensive range conditions and would depend upon the bulls' ability to locate the various subgroups.
 

Preference for a particular location

    It does appear that the 4 herds had preferred locations. This was particularly apparent for the green and blue herds but less so for red and yellow. This is quite well seen in the figure. Some groups were never observed in some locations while other groups were seen quite often. Another point to note is that locations 6 and 7 contained the source of drinking water and the use of these areas by all herds was expected. It is easier to assess the preference of the individual herds for specific locations by observing areas which lack such features.

    In discussion with local farmers the suggestion has arisen that there may exist a phenomenon of "home drift". This is taken to mean that in the late part of the grazing season, mixed community pasture herds may be seen to de-aggregate out of a large group, go back into their original home herd groupings and gravitate towards their home farms. If this were true it would beg several interesting questions such as what triggers the drift, is it poor pasture quality or forage availability, or lengthening nights? Also, how would cattle know which direction was home? Most of the cattle are trucked to the community pasture. Spatial orientation in cattle is an area about which next to nothing is known at present. These preliminary results appear neither to support nor to refute the notion of "home drift". Two of the herds (blue and green) did tend to cluster in regions of the field closer to their own farms, but since much of the field was not used by the animals at all there were few degrees of freedom here to test for significance. A process of clustering together as the season advanced was only apparently seen in the case of the red herd. Blue and green were apparently already clustered by the beginning of September and the yellow herd showed little tendency to cluster at all.
 

Implications of the findings:

    It is not entirely clear if all groups "drift" toward their home farm as the season advances, but if the observation has merit it could mean that the best way to maintain optimum pasture utilization would be to stock pastures with cattle from patrons who reside on all sides of the community pasture. Some community pastures join boundaries and patrons all lying in one direction may be forced to deliver to the same pasture. If the "drift" phenomena holds true this policy may need revision if the community pasture wants to optimize forage utilization and avoid clustering of cattle at specific "ends" of the pasture.