Recent Students

2024  Watson, K.L. Growth and shedding of harp seal (Pagophilus groenlandicus) vibrissae. M.Sc.

 The harp seal (Pagophilus groenlandicus) is the most abundant marine mammal in the 17 Northwest Atlantic. Climate change negatively affects the sea ice that the species needs for 18 pupping and moulting while also altering the composition and availability of the species’ prey. 19 Stable isotope analysis (SIA) is a non-invasive technique to determine dietary composition over 20 time and can be used to study dietary shifts that reflect changes in prey species availability. SIA 21 of facial vibrissae has been used to document dietary changes over time in seals. Knowledge of 22 growth and shedding of vibrissae is important for such research. In this study, I examined growth 23 and shedding patterns of mystacial vibrissae in three captive harp seals over one complete year. I 24 modelled vibrissa growth using von Bertalanffy growth curves that followed a non-linear, 25 asymptotic growth profile. Shedding occurred in 24/36 vibrissae across the three seals in March 26 and April, coinciding with the moult of body pelage in April and May. Most vibrissa growth 27 occurred in the first 100 days of the study (April–July); at this point, growth slowed and reached 28 an asymptotic length in approximately 150 to 250 days. Stable isotopes are deposited into the 29 vibrissa during the spring and summer. Dietary information includes the annual pelage moult, 30 feeding near the Grand Banks before migration, and potentially the migration to Baffin Island 31 and western Greenland, depending on variability in the timing of the migration. Asymptotic 32 vibrissa lengths varied greatly, so vibrissae in different positions could not be modelled using the 33 same von Bertalanffy parameter estimates. This research on harp seal vibrissae growth rates and 34 shedding patterns will be helpful to researchers applying SIA to study dietary patterns and shifts 35 due to environmental change.

 

2023  Salogni, E. Contest behaviour and offspring investment in female northern elephant seals(Mirounga angustirostris). Ph.D.  https://research.library.mun.ca/15907/

Parental characteristics and environment can affect survival and future reproductive success of offspring. In pinnipeds, mothers provide parental care by producing milk and protecting their young from other females. Contest behaviour and dominance structure of breeding females have been studied little in pinnipeds. I studied these subjects in breeding northern elephant seals (Mirounga angustirostris). The purpose of my research was to investigate maternal care, with emphasis on female behaviour in relation to social and physical environment, female social organization, and sexual-size dimorphism in pups.

I studied seals during the 2006-07 and 2007-08 breeding seasons at Islas San Benito, Mexico, near the southern limit of the species’ breeding range; almost all past research has been conducted at colonies in California. Through behavioural observations, I investigated relationships of aggressive behaviour to female morphological characteristics and their social and physical environment. Aggressive behaviour was positively related to female body size, presence of offspring, and density of females. I also provide the first description of dominance relationships and hierarchical structure in female pinnipeds using measures of orderliness and steepness (describing the transitivity of dominance hierarchies and the strength of the difference between individuals’ probability to dominate others respectively). I found the presence of weak to moderate dominance hierarchies and intermediate values of steepness. This new information contributes to our understanding of contest behaviour and the social environment, which may affect female reproductive success.

Finally, my study broadens general knowledge of breeding biology of northern elephant seals throughout the breeding range. I provide the first description of body size at birth and weaning at this colony of the species. My finding of similar body mass between the sexes at weaning in contrast with the great difference in adulthood implies that maternal care may have a negligible effect on adult body size or reproductive success.

My research will encourage research on female social structure in comparative studies on other pinniped populations and species, leading to more balanced knowledge and understanding of social dynamics and evolution in the group.

 

2018  Foley, J. Diets of gray (Halichoerus grypus) and harp (Pagophilus groenlandicus) seals in Newfoundland waters using hard-part and molecular analyses. Co-supervised by G. B. Stenson, Fisheries & Oceans Canada. M.Sc. https://research.library.mun.ca/13641/

I examined the diet of gray (Halichoerus grypus) and harp (Pagophilus groenlandicus) seals using: hard-part analysis (HPA; subdivided into stomach and intestine) and a multiplex Polymerase Chain Reaction (PCR) technique. Through these methods, I looked at harp and gray seal diet in Newfoundland waters, investigated otolith passage rates within the digestive tract, and developed a multiplex PCR technique to compare with HPA to further investigate biases associated with diet reconstruction based on HPA. Both techniques provided evidence for retention of large prey and faster passage of smaller pray. I conclude that otoliths of different sizes and thicknesses are affected by digestion differently; I suggest that HPA should be conducted using samples from both the stomach and intestine, and that it should be used in conjunction with other methods of diet analysis like PCR as this may give a better idea of the diet, and prey sizes consumed.

 

2018  Carmanico, L. Infection levels of two ascaridoid nematodes (Anisakis simplex and Pseudoterranova decipiens) in Atlantic cod (Gadus morhua) off Newfoundland and Labrador, and on the Flemish Cap. Co-supervised by G. B. Stenson, Fisheries & Oceans Canada. M.Sc. thesis.  (https://research.library.mun.ca/13188/)

Parasitic nematodes infecting the flesh of commercially important fish species pose an aesthetic and economic problem for the fishing industry. They also have potential health implications as they may cause disease in humans. The musculature of 811 Atlantic cod (Gadus morhua) from five cod stocks in the Northwest Atlantic off Newfoundland and Labrador, and on the Flemish Cap, were examined for two ascaridoid nematodes, Anisakis simplex sensu lato and Pseudoterranova decipiens sensu lato. I evaluated the distribution of these nematodes within the musculature of Atlantic cod, and investigated whether prevalence, abundance, or density varied among cod stocks or in relation to fish length. I used similar examination techniques to previous studies conducted during the 1940-50s and the 1980s, and compared infection levels to these studies. In all areas, prevalence and abundance of A. simplex s.l. increased substantially relative to historical studies. The highest infection levels of A. simplex s.l. were observed in fish from Northwest Atlantic Fisheries Organization (NAFO) Division 3M. The results are consistent with a possible increase in abundance of some cetaceans, the definitive hosts of A. simplex s.l.; although population trends of most cetaceans are not well known. In most areas, infection levels of P. decipiens s.l. also increased since the 1980s. The area with the highest abundance of P. decipiens s.l. was the west coast of Newfoundland (Divisions 3Pn4R). Greater abundances could be related to an increase in abundance of grey seals (Halichoerus grypus) that serve as definitive hosts. Major changes in marine food webs following the collapse of groundfish stocks in the late 1980s and early 1990s, as well asincreasing ocean temperatures, may also have influenced the population dynamics of these parasitic nematodes.

 

2016  Lawrence, C.T. Patterns of northern river otter (Lontra canadensis) habitat selection, diel activity, group size and activity at latrine sites in Newfoundland, Canada. Co-supervised by D. Cote, Parks Canada. M.Sc. thesis. https://research.library.mun.ca/12327/)

I investigated the presence and activity of northern river otters (Lontra canadensis) at latrines in relation to anthropogenic disturbances. I examined the validity of spraints as an index for latrine use and determined if diel activity or group size was related to anthropogenic disturbance. Latrine data were collected using boat surveys, and motion-activated camera traps were used to observe otter activity and group size. I found that disturbances such as logging, cabins or roads, did not differ between the locations of northern river otter latrine sites. However, the level of activity was higher at latrines that were distant from them. I found that spraint counts are not a good index for latrine use intensity, but there is potential for them to be useful when investigating otter abundance within a large landscape. Diel patterns of otters were not influenced by disturbances, but overall amount of activity was low in areas with disturbances meaning otters tend to avoid latrines in such areas.

 

2013  Hynes, D.P. A bioacoustic analysis of Red Crossbill (Loxia curvirostra) vocalizations from the island of Newfoundland, Canada. M.Sc. thesis. (https://research.library.mun.ca/10713/)

On the basis of morphological, ecological, genetic and vocal differences, North America Red Crossbills (Loxia curvirostra) have been described as a cryptic sibling species complex consisting of at least 10 forms. These forms are most easily differentiated via spectrographic analysis of their vocalizations and are hence known as "vocal types." However, little quantitative work has been done on forms' repertoires. For example, it is unclear if vocalizations, such as those named "excitement calls" or "chitter" by other workers, vary acoustically depending on the social context in which they are used or the physical state of the caller; it is also not known if such calls have characteristics that are taxonomically informative. Further, little is known about the vocal behaviour of Red Crossbills on the island of Newfoundland, an island which is generally presumed to contain the endangered Red Crossbill subspecies, L. c. percna. I made field recordings (~1000 minutes) of Red Crossbills at 10 sites on the island in order to describe and document structural and contextual variation in vocalizations and to determine categories of calls (Call Classes) that might contain systematic information useful for subsequent comparative analyses. Subjectively classified calls, made on the basis of the social, behavioural, and physical contexts of calling birds, audible qualities of calls, and general appearance of spectrograms, corresponded closely to those of crossbills (Loxia spp.) described elsewhere in North America and Europe. In total, adults uttered five Call Classes (I- HI, V and VI); juveniles uttered two (IV and V). Both adult males and juveniles of unknown sex also sang. Multivariate clustering of calls, based on the individual averages of 10 acoustic variables measured from 1186 calls, corresponded with the subjectively established Call Classes. Acoustic variability within individuals and across contexts was relatively low among Call Classes I and III. Call Class II was the most individualistic. A discriminant analysis (DA) on acoustic variables of Class I calls from Newfoundland individuals (n = 83) and individuals of vocal types from elsewhere in North America and Europe (n = 31) classified 89% of birds to the correct vocal type; 98% of birds from Newfoundland were differentiated successfully by DA. Further, many birds from Newfoundland also emitted Class III calls and song motifs that were distinct. Visual examination of Class I spectrograms, including those individuals misclassified by DA, confirmed that seven individuals from Newfoundland were spectrographically and audibly more similar to vocal types 2 and 10, which have been described previously on mainland North America. Thus, the results of this study show that multiple Red Crossbill forms, possibly including L. c. percna, are present on the island of Newfoundland.