Regulation of breeding expenditure in the blue-footed booby, Sula nebouxii : an experimental approach

González‐Medina, Erick; Castillo-Guerrero, José Alfredo; Santiago‐Quesada, Francisco; Villegas, Auxiliadora; Masero, José A.; Sánchez‐Guzmán, Juan M.; Fernández, Guillermo

doi:10.1016/j.anbehav.2015.06.025

Cited by 12 publications

(14 citation statements)

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“…By measuring the effect of an expenditure on leucocyte profiles, its physiological cost can be assessed (e.g. Gladbach, Gladbach, & Quillfeldt, ; Gonzalez‐Medina et al., ; Hegemann, Matson, Flinks, & Tieleman, ; Wojczulanis‐Jakubas, Jakubas, Chastel, & Kulaszewicz, ). For example, Gonzalez‐Medina et al.…”

Section: Use Of Leukocyte Profiles Over the Past Decadementioning

confidence: 99%

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The use of glucocorticoid hormones or leucocyte profiles to measure stress in vertebrates: What’s the difference?

2018

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Measuring stress in animals is important in many ecological, zoological and veterinary research settings. A common method is to measure plasma levels of glucocorticoid hormones (cortisol, corticosterone, hereafter CORT). Over the past decade, an alternative method has become widely popular: assessing leucocyte profiles; in other words, the heterophil‐to‐lymphocyte ratio (H/L) in birds and reptiles or the neutrophil‐to‐lymphocyte ratio (N/L) in mammals, amphibians and fish. Recent studies have shown that although both indices reliably change after acute stress, they are not always correlated at baseline, and thus are not interchangeable. This lack of correlation has led to some confusion about which of these two measures is “better”; in other words, more biologically relevant and a truer readout of stress. In this review, we first document the dramatic expansion of the use of leucocyte profiles to assess stress over the past decade. We then review published evidence that may explain the discrepancies between leucocyte profiles and plasma CORT. We argue that these discrepancies stem from the nature of the stress reaction and the role of corticosterone (or cortisol) versus leucocytes during the stress response. The differing roles of the two responses translate to differences in the timing of each, which is important for researchers studying either acute or chronic stress. Although plasma glucocorticoids rise within minutes of the onset of acute stress and return to baseline within 1 or 2 hr after the stressor passes, H/L or N/L ratios remain low for at least 30–60 min or sometimes more. The temporal nature of these metrics differs also in the context of long‐term chronic stress. The glucocorticoid response wanes in repeatedly stressed animals, or those exposed to chronic environmental stress, which can often (but not always) lead to low baseline levels and more typically, an attenuated acute stress response. Meanwhile, H/L or N/L ratios appear to remain high under the same conditions. Understanding the temporal differences in the responses should help researchers decide which metric is the better method in their particular study, or whether both would be useful for elucidating different elements of the stress response.

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Section: Use Of Leukocyte Profiles Over the Past Decadementioning

confidence: 99%

“…For example, Gonzalez‐Medina et al. () manipulated brood size in blue‐footed boobies Sula nebouxii , a long‐lived seabird. They found that increased parental effort resulted in increased foraging effort along with an increase in H/L ratio.…”

Section: Use Of Leukocyte Profiles Over the Past Decadementioning

confidence: 99%

The use of glucocorticoid hormones or leucocyte profiles to measure stress in vertebrates: What’s the difference?

2018

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“…Thus it appears that the adjustment made by parents was sufficient to maintain reproductive value, so the senior chicks did not trigger the removal mechanism for junior chicks (González‐Medina et al . ).…”

Section: Discussionmentioning

confidence: 97%

“…Parents modified their foraging expenditure in response to variation in the food demand of the brood, making more foraging trips and decreasing their time at the nest when parental reproductive demand was increased (Gonz alez-Medina et al 2015). These foraging adjustments, however, may have partially compensated for the reproductive expenditure because offspring from broods in which reproductive expenditure was experimentally increased showed some physiological costs (lower BCI and ALP levels and higher H/L ratios than controls).…”

Section: Body Condition Index and Survival Ratementioning

confidence: 99%

“…Blue‐footed Booby parents from this experiment showed short‐term adjustments in foraging behaviour (foraging effort and time at nest) in response to increasing or decreasing chick food demand, and these adjustments were reflected in the physiological status of parents (creatine kinase/total protein and H/L ratios) (González‐Medina et al . ). These results suggested that both parents were willing to adjust their reproductive expenditure in order to maintain the value of the brood.…”

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confidence: 97%

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Variation in parental rearing expenditure triggers short‐term physiological effects on offspring in a long‐lived seabird

González‐Medina

Castillo-Guerrero

Santiago‐Quesada

et al. 2016

Ibis

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Parental care in long-lived bird species involves a trade-off between the benefits of increasing the effort expended on current offspring and the costs that this represents for future reproductive output. Under regimes of high environmental variability, long-lived seabirds can adjust their breeding effort to buffer the negative effects of this variability on their offspring. However, the potential impacts of variation in breeding effort on offspring physiology in the short term and on longer-term survival are poorly understood. In this study, we manipulated brood age through a cross-fostering experiment to assess whether increasing or decreasing parental reproductive expenditure led to costs in Bluefooted Booby Sula nebouxii chicks. Specifically, we tested the consequences of altered parental reproductive expenditure on the offspring's physiological condition (plasma metabolites, heterophil to lymphocyte ratio (H/L) and body condition index (BCI)) and survival. Offspring from broods in which parental investment was experimentally increased showed a lower BCI and lower alkaline phosphatase levels and higher H/L ratios than controls. Conversely, offspring showed the opposite pattern when reproductive expenditure was experimentally decreased. We observed no effects of manipulation of parental investment on triglyceride levels or on survival rates. Although our findings suggest that Blue-footed Booby parents have the ability to adjust their breeding effort according to the demands of their offspring, parental effort could influence the effect of hatching order by suppressing the aggressive tendency of the senior chick.

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Flexibility in food resource allocation in parents and selectivity for offspring: variations in δ15N and δ13C values during breeding of the blue-footed booby

et al. 2017

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Regulation of breeding expenditure in the blue-footed booby, Sula nebouxii : an experimental approach

Cited by 12 publications

References 50 publications

The use of glucocorticoid hormones or leucocyte profiles to measure stress in vertebrates: What’s the difference?

The use of glucocorticoid hormones or leucocyte profiles to measure stress in vertebrates: What’s the difference?

Variation in parental rearing expenditure triggers short‐term physiological effects on offspring in a long‐lived seabird

Flexibility in food resource allocation in parents and selectivity for offspring: variations in δ15N and δ13C values during breeding of the blue-footed booby

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