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Satellite tagging has greatly improved understanding of whale distribution, migration and habitat use. However, all large whale satellite tags are invasive to some extent and concerns have been raised about possible adverse effects on individuals. Additionally, most tags do not achieve their expected transmission life and the reason for these premature failures is rarely known. A followup study was conducted in the Gulf of Maine from 2011-2015 to assess tag performance and impacts in North Atlantic humpback whales (Megaptera novaeangliae). Sixty-five Type I satellite tags were deployed on well-studied individuals with strong prior residency characteristics and known demographic traits. Short-term responses to tagging were assessed during a one-hour focal follow and a control sample was established from comparable whales that were also identified in the tagging area. Tagged whales were regularly re-encountered to assess the state of the tag, tissue responses and the overall condition of the whale. Follow-up monitoring was conducted through dedicated research platforms and the opportunistic contributions of a collaborating network of commercial whale watching operations. Etchings on the tag transmitter housing allowed for visual assessments of egress over the lifespan of the attachment, while photogrammetry provided data on depth of tag penetration, the size of exit wounds and some tag site responses. A scoring system was developed to quantify tissue responses at the tag site and statistical modeling was employed to identify variables potentially responsible for a range of host responses. Mark-recapture statistical analysis was used to compare survival, detection probabilities and calving probabilities of tagged whales and controls. Telemetry data was obtained to increase understanding of the humpback whale movements, habitat use and human impacts in the Gulf of Maine. This was a designed study of tag performance and impacts and it has yielded new information on all of its primary objectives. These included assessments of the following: 1) physical and physiological responses to satellite tags; 2) deployment and design factors as they relate to tag performance and the potential for impact on tagged individuals; 3) behavioral responses to tagging, including the potential for post-tagging shifts in distribution; and 4) movements and habitat use of humpback whales in the Gulf of Maine. One of the most significant outcomes of this study was the detection and correction of multiple design flaws in tags that had been previously tested and used widely in the field. One involved a feature that was common to a range of tagging projects conducted over the past 10 years, and it is possible that similar failures have occurred previously but were not documented. Repairing these designs over the course of the study resulted in increased tag transmission durations, reduced tag-related tissue responses and may have resolved a sub-lethal impact on reproduction. These findings confirm that even with prior testing and wide use, Type I tags do not necessarily perform as designed. Given the number and nature of the flaws that were detected, fully integrated tag designs may be the most appropriate way to minimize the risk of Type I tag breakage and associated injuries. Extensive follow-up observations over multiple years allowed for an examination of a range of host responses to Type I tagging, including: behavior, tag site responses and vital rates. Prior studies have not studied these varied facets of tag response in an integrated manner. Gulf of Maine humpback whales were relatively resilient to the tag designs and deployment practices applied in this study, at least through the observations made to date. Tagged whales had a high survival rate and tag site tissue responses tended to diminish over time. Females were less likely to calve in the first year after tagging than females that were not tagged, but this effect may have been related to breakage versus proper tag function. One of the most consistent predictors of host response was the location of the tag on the body, which appeared to influence both tag site tissue responses and animal behavior. Although our results must still be validated in other species, they suggest that deployments that target the upper flank near the dorsal fin are least likely to produce a negative effect. Contrary to other studies, tagged whales exhibited pronounced immediate and extended behavioral responses to tagging, and the latter may have affected the telemetry data after tagging. We recommend monitoring behavioral responses at the time of tagging, as well as additional research to better understand the biological meaning and implications of the wide range of behavioral responses observed. This study highlights importance of follow-up studies to evaluate and improve satellite tagging technology. Although the level of observer effort may be difficult to replicate in other areas, the methods employed can be extended to other species and populations. Continued efforts to develop more robust and benign anchoring systems would enhance the scientific value of this technique and reduce risks to tagged individuals.