Table 5. Properties of solid biomatrices with regard to measurement of cortisol and corticosterone.

Properties	Solid biomatrix
	Hair	Feathers	Nails/claws/ hooves	Scales
Invasiveness of sampling	Low [82,83]	Low	Low [71,84]	Low [71,85]
Risk of contamination from external sources	Yes	Yes	No	No
Training required for sampling procedure	No [57]	No [40]	No	No
Sampling procedure may confound results	No	No	No	No
Possibility of repeated sampling	Yes	Yes	Yes	No
Ethical and legal licenses required	Yes	Yes [40]	No	Yes [85]
Biosecurity concerns	Low	Low [86]	Low	Low
Results depend on time of sampling	No [87]	No [40]	No	No
Results depend on sampling location	Yes [57]	Yes	No	No
Steroid medications may confound results	No	No	No	No
Sampling requires live animals	No	No [86]	No	No
Sample preparation is laborious and time consuming	Yes	Yes	Yes	Yes
Storage conditions	Room temperature [87]	Room temperature [40]	Room temperature [84]	Refrigerator, freezer [85]
Time range represented by biomarker measurement	Week, month, year	Week, month, year	Week, month, year	Week, month, year
Biomarker forms represented	Unbound [88]	Unbound [88]	Unbound [88]	Unbound [88]
Stress type	Chronic [82,83]	Chronic [67,86]	Chronic [71,84]	Chronic [71,85]
Analytical cost	Relatively inexpensive [72]	Relatively inexpensive [40]	Relatively inexpensive	Relatively expensive